Scandisk

This is something that Windows 98 users will use from time to time to help fix errors on their disk, thankfully Windows XP has improved enough where the scandisk will only happen during serious failures and only happen during startup...mainly this is because of the NTFS file format, but, you don't need to know that at the moment. If you're in Windows 98 this is how you do a scandisk:

Go to Start--->Accessories---->System Tools--->Scandisk...once you do this you'll open up a program that will give your computer a quick scan in order to find a file format problem, lost clusters, corrupt clusters, etc. You can run a standard which will check the files and a thorough that will scan the hard disk for physical errors.

If you're a Windows 98 user and you run into hard drive troubles or any computer troubles remember to give scandisk a try, it might solve the problem. I underline might because I used Win 98 for years and scandisk only solved the problem once, so...keep in mind that it is not the be all and end all to computer repair.