Check disk under windows XP

Also try running chdsk on your harddisk, assuming you only have a c: drive, do this:

click start, run, type in cmd, that brings up a dos window,
type in: chkdsk c: /i /c [there is a space between chkdsk and c: and between c: and /i and between /i and /c ]

hit enter, see if any errors are reported, you will need to add one thing to that to fix them, like this:

chkdsk c: /f /i /c

the /f will fix errors, but don't do it until you are sure you need to, if you have errors in certain places and they get fixed your system might not run.