China DOS Union

Complete Manual for Repairing Hard Disk Soft Failures

Maintenance Tools

　　As the saying goes: if a worker wants to do his job well, he must first sharpen his tools. In everyday use, we should become proficient with several kinds of hard disk maintenance tools, so that when we run into hard disk soft failures we won’t get confused and panic. Below I will briefly introduce the use of several hard disk maintenance tools for common hard disk soft failures.

　　★ Repairing the hard disk master boot record ★

　　If the hard disk master boot record and partition table are damaged due to virus destruction or operational mistakes, the hard disk will not be able to boot.

　　① KV3000

　　As a well-known antivirus program, KV3000 also has very powerful master boot record and partition repair functions. We can first boot with a floppy disk, then run KV3000 and press the F6 key to view the hidden sectors of the hard disk that can no longer boot, that is, to check whether the master boot information in hard disk head 0, cylinder 0, sector 1 is normal. If in hard disk head 0, cylinder 0, sector 1, the key codes cannot be found, namely the hard disk partition table key codes “80” and “55 AA”, then the hard disk itself cannot boot, and even after booting from a floppy disk it still cannot enter the hard disk. At this time, you can press the page keys PgDn or PgUp to search within the hidden sectors of the hard disk. If found, flashing red “80” and “55AA” will appear in the table, along with a beep to notify you, and the following line will show a prompt: “F9 = Save To Side 0 Cylinder 0 Sector 1 !!!”. At this time, press the “F9” key once, and the original hard disk master boot information just found, that is, the information displayed in the table, can be written over hard disk head 0, cylinder 0, sector 1. Then the machine will reboot from the hard disk and restore its boot capability.

　　② FDISK

　　Use FDISK/MBR to overwrite the code area of the master boot record, but it does not rebuild the primary partition table. It is suitable for cases where the master boot record has been damaged by a boot-sector virus or the master boot record code has been lost, but the primary partition table itself is not damaged. Note: FDISK/MBR is not suitable for removing all boot-type viruses, so use it with caution.

　　③ FIXMBR

　　FIXMBR is a small tool specifically used to reconstruct the master boot sector, and it is also simple to use. If you run FIXMBR directly, it will check the MBR structure, and if it finds the system abnormal it will ask whether to repair it. If you answer “YES”, it will search the partitions. After finding the corresponding partition, the system will ask whether to modify the MBR; answer “YES” and it will begin automatic repair. If the search result is wrong, you can use the /Z switch, and after restarting the system it will return to the original state. If you want to know the usage of FIXMBR in detail, you can use the /H switch to view it.

　　★ Repairing the hard disk partition table ★

　　① KV3000

　　In the main menu of KV3000, press the F10 key to quickly test relevant system parameters and the hard disk partition table. If the hard disk partition table is abnormal, KV3000 will first save the bad partition table to a floppy disk as a precaution, then automatically rebuild the hard disk partition table and bring the hard disk back to life.

　　But if the hard disk has only one partition, and the file allocation table (FAT table) and file directory table (ROOT table) are seriously damaged so that all data is gone, then even if this function restores the partition table of drive C, it still cannot make drive C boot, nor can it recover the data. At this time, other hard disk repair tools are needed together to recover the data. If the hard disk still has partitions such as D, E, ... and so on, then in general KV3000 can recover the later partitions that have not been damaged, rebuild a new hard disk partition table, and then after booting the machine with a DOS system floppy disk, you can enter the later partitions on the hard disk, back up the data, and then repartition and format the hard disk.

　　For detailed instructions on how to use KV3000 to repair hard disks, everyone can check the instructions file of the KV3000 antivirus software, or go to the Jiangmin website to look it up.

　　② FDISK

　　FDISK can also be used to create new partitions and rebuild the primary partition table, but this method does not overwrite the code area of the master boot record. If you want to ensure that the data inside the hard disk is not damaged, the partitioning must match the original partitions, otherwise the data will be lost. I won’t ramble on about the specific method here; I suggest everyone use the Chinese-localized version of FDISK, which is very easy to get started with.

　　③ DiskMan

　　What makes DiskMan outstanding is its hard disk partition table recovery function, and it uses a graphical interface, representing the detailed structure of the partition table in chart form. For details on how to use it, see “A Small Tool That Never Gets Old—DiskMan”

　　★ Recovering a hard disk FAT (file allocation table) and DIR (root directory table) ★

　　If the FAT table is damaged, all files may be lost. Even for someone very proficient in DOS, repairing files on a disk with a damaged FAT table is not an easy task.

　　① NDD（Norton Utilities 8.0）

　　Start NDD, the disk repair program in the NU toolkit. In its menu, choose Options/General to confirm that NDD will carry out a comprehensive check including the master boot area and CMOS, then in the main menu choose Diagnose Disk to diagnose the hard disk. When NDD finds errors it will automatically report them, and prompt with an error description (Description) and recommendation (Recommendation). You can decide whether to repair according to the situation. When repairing, remember to save an UNDO disk so it can be used to restore operations if needed. During the repair process, especially during the surface test (Surface Test), if it reports read/write errors, that means the hard disk has physical damage and data may be lost.

　　After diagnosis and repair are finished, restart the computer. If you can access drive C, then the job is done, and you can simply restore hard disk functionality by backing up the data and reinstalling the operating system. Otherwise, you can only perform a restore operation (UNDO), and try manual recovery or other methods. But NDD（Norton Utilities 8.0）can only run under DOS, and does not support FAT32 format.

　　② SCANDISK

　　A hard disk checking tool similar to NDD that comes with Microsoft operating systems. It should be familiar to everyone, because after an improper shutdown in WIN 9X, when we restart it will automatically run and scan the hard disk. Its usage is somewhat similar to NDD.

　　③ CHKDSK

　　Likewise, this is a tool that comes with Microsoft operating systems, specifically used under DOS to check hard disks. The CHKDSK/F command format is specifically used to recover lost clusters on the hard disk and free lost hard disk space. Sometimes we can find some important data in the *.CHK files generated after it runs.

　　The FAT table and root directory of a hard disk constantly change as users write and delete files. If you can frequently back up the FAT table and root directory, then when the FAT table is damaged, writing back the FAT table and root directory can restore the hard disk to the state it was in at the last save. When the FAT table or root directory of the hard disk is damaged and the saved FAT table and root directory data need to be written back, the starting logical sector number and length (number of sectors) of the FAT table and root directory must be correct.

　　★ Recovering a partition deleted by mistake ★

　　① FDISK & formAT

　　If no other partition operation has been performed after a partition was deleted by mistake, then following the method below will generally restore the original data: run the FIDSK partitioning program and rebuild the deleted partition, but be careful to keep the partition size and position the same as before; restart the system into MS—DOS mode, then run “format X:/u/q” (X is the drive letter of the mistakenly deleted extended partition). At this time the system will first warn: “This is a large hard disk, if formatted, all data will be lost.” At this point choose “YES”; then the system will tell you that the partition cannot be quick-formatted and ask whether to perform a “full format”; answer “NO”. The key to this step is adding the /q parameter (quick format). After doing this “fake format” once, if nothing unexpected happens, you should be able to access the data in that partition.

　　In addition, partitions recovered by this method may become inaccessible again after the next reboot. Although the data can still be recovered by the above method, we recommend that after recovering the partition you back up all data in it, and then carry out a complete formatting process.

　　★ Rescue for damage to hard disk track zero ★

　　① DE （PCTOOLS 9.0）

　　If running ScanDisk to scan drive C shows a red “B” in the first cluster, that means drive C has damage in track zero! Run DE under DOS. First enter the Options menu, choose Configuration, and press the space bar to remove the “√” mark in front of Read Only (read-only mode) (press Tab to switch), then save and exit. Next choose Drive in the Select menu of the main menu; after entering, in the Drive type item choose Physical, press the space bar to select it, then press Tab to switch to the Drive item, select hard disk, then choose OK and press Enter. After that, return to the main menu and open the Select menu. At this time Partition Table will appear; select and enter it, and then you can see the hard disk partition table information. For example, if the hard disk has two partitions, then in the hard disk partition table information we can see that partition 1 is drive C, and that partition starts from cylinder 0 of the hard disk. Then changing the Beginnig Cylinder of partition 1 from 0 to 1 will do. Save and exit. Restart and enter BIOS, run automatic hard disk detection, and you can see that the units digit of CYLS is reduced by one (for example: 782→781). Save and exit, repartition and format, and the job is done.

　　But DE does not support FAT32 format and only runs under DOS, and PCTOOLS 9.0 is not so easy to find nowadays. Back in the day, together with Norton Utilities 8.0, it was one of the two outstanding flowers among utility software...

　　② PQMAGICT

　　The famous Partition Magic (Partition Magician) is probably the hard disk partitioning tool most commonly used by everyone. PQMAGICT is its DOS version tool, and using it to repair a damaged hard disk track zero can be said to be as easy as turning over your hand.

　　Suppose a hard disk has two partitions (C, D). Using ScanDisk to check drive D shows that drive D has damaged track zero, so formAT cannot format it. If you use FDISK to readjust the size of logical drive D so that the logical track 0 of drive D moves forward or backward, crossing over this bad track, then all the data on drive C will be destroyed. Therefore at this time we must rely on the power of PQMAGICT. First start PQMAGICT under DOS (you must first COPY PQ to drive C), choose to view drive D, and at this time the screen will display the partition and capacity information of drive D. Then choose Reszie Selected Partition in the Option menu, drag the capacity scale on the left with the mouse so that the D partition becomes a little smaller, or directly manually enter the capacity size assigned to the D partition. The purpose is to leave the bad area unused. After confirming, PQMAGICT will begin converting the D partition, and after completion exit PQMAGICT. This way the files on drive C are left completely untouched, and drive D sees the light of day again.

　　② SPecialFDisk

　　When creating a primary partition, SPecialFDisk allows the user to define the starting cylinder, so it can skip over a damaged cylinder area. This trick is one of SPecialFDisk’s killer moves. For how to use it, please see “A Small Tool That Never Gets Old—SPecialFDisk”

　　★ Rescuing a hard disk locked by a “logical lock” ★

　　① DM

　　A hard disk hit by a “logical lock” cannot boot normally from floppy disk, CD-ROM, or dual hard disks, but we can use the software DM to unlock the hard disk. Because DM is a hard disk tool that does not depend on the motherboard BIOS recognizing the hard disk, even if the hard disk is set to “NONE” in the motherboard BIOS, DM can still recognize the hard disk and perform operations such as partitioning and formatting. First, you need to copy DM to a system disk. After connecting the locked hard disk and powering on, press the DEL key to enter BIOS setup, and set the IDE hard disk to “NONE” (this is the key point!). Save the settings and exit, and the system can then boot “with the lock.” After booting, run DM, and you will find that DM can recognize the hard disk. Select that hard disk and partition and format it. However, the weak point of this method is that all data on the hard disk will be lost.

　　The causes of hard disk soft failures are rather complex. Viruses, accidental operations, and even an unexpected power loss may cause the hard disk to crash. Therefore, you should develop the habit of backing up important hard disk data in normal times, so that when the critical moment comes, the problem can be solved smoothly.

　　Analysis and troubleshooting~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

　　Hard disk failures can generally be divided into two broad categories: hard failures and soft failures. Hard failures mean damage to the PCBA board, scratches on the platters, damage to the head voice coil motor, and so on. Because repairing hard failures requires a relatively high level of basic knowledge and repair conditions, and must be handled by professional technicians, they will not be discussed in this article.

　　Soft failures are failures caused when the data structure of the hard disk, for some reason such as a virus, becomes disordered or even unrecognizable. Generally speaking, if the motherboard BIOS hard disk auto-detection (IDE HDD AUTO DETECTION) function can detect the hard disk parameters, then it is a soft failure.

　　Generally, when a hard disk fails, the system will display some prompt information on the screen, so we can find the cause of the failure according to the prompt information shown on the screen and implement a targeted solution.

　　★ Common hard disk boot error messages and analysis/handling ★

　　① Non-System disk or disk error，replace disk and press a key to reboot （non-system disk or disk error）

　　One cause of this message is lost CMOS parameters or an incorrect hard disk type setting. Just enter CMOS and reset the correct hard disk parameters. The second is that the system boot program is not installed or has been damaged. Transfer the boot files again and install the system program.

　　② Invalid Partition Table（invalid partition table）

　　This failure is generally caused by errors in the partition table in the hard disk master boot record. When multiple active partitions are specified (there can only be one active partition), or when a virus occupies the partition table, the above prompt will appear.

　　The master boot record (MBR) includes three parts: the boot program, the partition table, and the ending marker “55 AA”, occupying a total of one sector. The master boot program contains program code for checking the hard disk partition table, along with error messages, error handling, and so on. When the hard disk boots, the master boot program checks the boot flag in the partition table. If a partition is bootable, it has the partition flag “80”; otherwise it is “00”. The system specifies that only one partition may be a boot partition. If the partition table contains multiple boot flags, the master boot program will give the “Invalid Partition Table” error prompt. The simplest solution is to repair it with a hard disk maintenance tool. For example, use NU 8.0 NDD to repair it. It will check for errors in the partition table, and if errors are found, it will ask whether you want to modify them. You only need to keep answering “YES” to correct the errors. Or you can overwrite it with a previously backed-up partition table. If the partition table has been infected by a virus, even high-level formatting will not solve the problem. You can first use antivirus software to remove the virus, then use a hard disk maintenance tool to repair it.

　　If the above methods still cannot solve it, you can also use FDISK to repartition, but the partition size must be the same as the original partition. This point is especially important. After partitioning, do not perform high-level formatting, then use NDD to repair it. This both ensures that the hard disk can boot after repair, and that the data on the hard disk will not be lost. In fact, using FDISK to partition is equivalent to overwriting the original partition table with a correct partition table. This trick works especially well when the hard disk is not recognized after booting from a floppy disk.

　　③ Error Loading Operating System（error loading DOS boot record）

　　Missing Operating System（DOS boot record damaged）

　　This failure is generally caused by an error in the DOS boot record. The DOS boot record is located in logical sector 0 and is generated by the high-level formatting command formAT. After the master boot program verifies that the partition table is correct, it reads the DOS boot record according to the starting address of the DOS partition indicated in the partition table. If it fails five times in a row, it gives the error prompt “Error Loading Operating System”; if it reads the DOS boot record correctly, the master boot program will load the DOS boot record into memory at 0:7c00h, then check whether the last two bytes of the DOS boot record are “55 AA”. If they are not, it gives the message “Missing Operating System”.

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Bump

Good stuff, I’ll save this first.
Question: there are some tools that can edit disk sectors, but I don’t know the correct way to operate them. Could an expert explain it a bit? Many thanks in advance.

Question for all the experts:

When booting from the hard disk, text like emdisk appears and it prompts an i/o error, and it cannot boot.
What is the reason? How can it be solved?

Sure enough, practical and comprehensive. Thanks first!!

Why does the last problem only explain the cause, without giving a solution?

Hello, the analysis is very good, but I’d still like to ask one more thing: when "disk boot failure insert system disk and press enter" appears, can you analyze that? Thanks

笔武:
"disk boot failure insert system disk and press enter"
Disk boot failure, please insert the system floppy disk and press Enter.
Analysis??

When the error message “Patition's drive letter cannot be indentified” appears, Partition magic cannot be run. What tool should be used, and how can this be solved???
--I also hope all you experts won’t hold back your advice