There are many posts about it. But all contain what's in this article -> http://support.microsoft.com/?id=222469
In closing, ALL machines I've ever encountered were cured with that article.
When I try to run scan disk, a message keeps coming up telling me that Windows is running a program in the c drive, and that i should exit all running programs. the problem is that i am not running any programs while i am running scan disk. it also will not let me do a defrag. i am ready to pull my hair out. any suggestions?