China DOS Union

On a Win98 machine, I ran a file under DOS (dskwrite.exe extracted from the downloaded miniWindows3). In the middle it gave a prompt saying something like “File allocation table error on drive C” (roughly that meaning, I don't remember clearly; now it doesn't even show that prompt anymore), and then the hard drive became inaccessible. But in the BIOS parameter settings the drive can still be detected. Booting from a system floppy still can't access the hard drive either, prompting “Invalid drive specification”; scandisk c: on the floppy won't run either; scanreg on the floppy says there is a problem with HIMEM; Safe Mode etc. all switch to a:; fdisk /mbr is also useless; using fdisk to view the partition status shows the types of all four partitions as non dos. Mounting this hard drive on another machine gives the same result.
Did dskwrite.exe modify track 0 of the hard drive? The original data must be kept—what should I do?

The hard drive partition table is damaged. Use advanced partition software to restore it (disgen ,spfdisk ,pqmagic .....)

Use KV300. Press F6, and you can view the hidden sectors of a hard drive that can no longer boot, that is, check whether the boot information in hard disk 0, head 0, cylinder 0, sector 1 is normal. The master boot information is the starting point of hard drive booting. The two more important markers are 80H and 55AA. They indicate that the system is bootable, and in the entire partition table there can only be one 80H marker; the other is the ending 55AA marker, which indicates that the master boot information is a valid record. In addition, each partition's own boot information also ends with 55A. If the key code is not found in head 0, cylinder 0, sector 1 of the hard drive, then the hard drive itself will not be able to boot on its own, and even after booting from a floppy it still cannot enter the hard drive. You can search within the hidden sectors of the hard drive. After finding it, the system will automatically show flashing red “80” and “55AA” in the table and give a beep to notify you. The bottom of the screen will prompt “F9＝Save To Side 0Cylinder 0 Sector 1!!!”. At this time, press the “F9” key, and the original hard drive master boot information just found can be written back over head 0, cylinder 0, sector 1 of the hard drive. Then the computer will reboot the hard drive and restore its boot capability, and after booting from a floppy you will also be able to enter the hard drive.
After booting the system from a floppy, run KV300 and press the “F10” key to quickly test relevant system parameters and the hard drive partition table. If the hard drive partition table is abnormal, KV3000 will prompt you to first save the damaged partition table to the floppy in case the operation fails, and then automatically rebuild the hard drive partition table, bringing the hard drive back to life.
I once used this function and recovered all the data, but it took an insanely long time.

Problem solved! Used kv300 + EasyRecovery.
Special thanks to tdj for giving me the crucial pointer;
Special thanks to dos时代菜鸟, who guided me out of the maze late at night, and was even an mm!

Just rebuild the master boot record in diskman.

The gentleman in the post above is right. This problem can be fixed with diskman; diskman is a small but powerful program written by a Chinese author.