You can also get the free ScanDefrag. It is the most advanced disk maintenance program there is. It runs Disk Cleanup, ScanDisk, and Disk Defragmenter.
It's easy to setup and use, and it can deal with problems like "drive's contents have changed: restarting...".
Get it and read about all the options it has that you can use. It is a small download.
http://home.earthlink.net/~bblanton2/scandefrag/main.htm
http://www.blueorbsoft.com/scandefrag/index.html
First configure Disk Cleanup (tick all options), then ScanDisk (as suggested by ScanDefrag) and at last Disk Drefagmenter.
Click RUN and let the process finish. If the HDD is as messy as it sounds, it may take a while to finish the 3 processes, but be patient, it will pay back.
Zee
I have a Sony Pentium II 400 Computer, Windows 98 OS. My system is configured for 2 hard drives (C & D). I am having problems with my C drive. I cannot run Defrag; it starts over and over again. Defrag runs to completion on the D Drive. I tried to run scan disk and check/unchecked option to fix errors automatically.
I have event tried running defrag by first going to msconfig and setting options from normal to select.
I think the hard drive is just about gone now. I'm beginning to have missing links (pictures, hyperlinks) on web pages occasionally.
.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic