See if it will let you boot to "safemode"....after you reboot...watch for the loading screen to tell you to hit F8 for more options & do so...then pick safemode...if it then boots in safe....go to "Start/run/...& type in the following....sfc /scannow, & hit enter. There is a space between sfc & / or it won't come up. have your 2000 disk handy to insert as it will tell you to do this. This checks the file system for errors & if thats the problem it will rewrite the files from the disk. I have this come up occasionally...I just scan & repair.
If this doesn't do the trick...then boot from your CD..& use the repair option....if this doesn't work...let me know...I'm an old hand with 2000!!