At first, the computer froze when surfing the Internet. Then when I restarted, I couldn't boot into Win98. I estimated it was infected with a virus because there wasn't much on my C drive. I was going to format the C drive and reinstall the system. There were some files on my desktop. I first used the Win98 boot disk to enter the C drive and copied these files to the E drive. Then I originally wanted to format immediately, but then I thought maybe antivirus would fix it without formatting. I used Kav9x to kill the virus (I installed Kingsoft Antivirus), but it prompted that it couldn't run under DOS. Then I accidentally ran Kavdx, and it seemed like the computer started virus scanning. I took a look and then exited. Then I restarted the computer (without inserting the boot disk), and "scandisk" appeared (it seemed like that). I waited and then got a prompt that it seemed like the hard drive couldn't be found (I don't understand much, that's the general meaning). Then I pressed Enter and the machine continued to boot to my desktop (I thought it was okay because the things on the desktop appeared, just like normal boot). But after 2 seconds, it froze. The mouse could move but couldn't be clicked. Then a bunch of various error prompts appeared (many prompt boxes), and it couldn't be operated, so I could only restart. Then I was going to format, but I couldn't enter with the Win98 boot disk. After the machine self-tested, the floppy drive light was on, proving it was reading the disk, but after a few seconds, there was no response. The hard drive also had no response, just stopped there, and it's been like that all the time. The next day I went to a classmate's place to fix it (because I don't understand, I'm a novice). The classmate first hung my hard drive and his hard drive at the same time (my hard drive was the slave drive), but my hard drive couldn't be found. Then with only my hard drive left, the classmate could enter DOS with the Win98 boot disk. But when formatting the hard drive to 3%, it prompted that there seemed to be bad sectors on the hard drive, and then it started automatic detection. Because it took too long, I exited halfway. (At this time, the classmate didn't know what to do either. He wanted to low-level format. I said to take a look again, in case it could be solved without destroying the data.) And I thought my Win boot disk was problematic, so I made a new one. Then I was going home to try it and see. (And at this time, the classmate's hard drive also prompted bad sectors. When I left, the classmate was still detecting.) But after going home, I still couldn't enter DOS, the same as before, stopped at self-test and didn't move. And when I didn't insert the boot disk to boot, after self-test, a prompt message appeared (I can't remember clearly, it seemed like there were words like CD-ROM, DMI. I'll check when I get home and write it down again.) That's the specific thing. What might be the reason? What should I do? I want to try low-level formatting, but I'm afraid that if it's not a hard drive problem, all the data inside will be lost. I heard that CIH can cause physical damage to the hard drive and motherboard. So I want to ask you all. I'm almost an idiot about BIOS and CMOS. So if you need me to make changes to the settings of these things, please teach me specifically. Thank you everyone!!!