Problems using scandisk in Windows XP and 2000

[Celftic]

I have a problem with my computer when I try to use scandisk it tells me to restart in order to do it. I had WinXP for over a year and it only started doing this like 2 weeks ago (see the image below) Every time I restart that is what I see, I had windows XP but I reformated to windows 2000 to try to see if that fixed the problem but it didn't. This is strange, I can't use scandisk! My sister got a new hard drive, the same as mine (Western digital 8MB cache) and hers does the same thing. Anyone know how to fix it?

http://img20.imageshack.us/img20/1073/Image115.jpg