i too had this prob in win xp.. if u r usin xp do this..
start-run-command
there type
fsutil dirty query C: (do the same for all partions)
if it shows drive is dirty
type chckntfs\d and press enter.
then exit command and restart the computer.leave it to chck for errors and fix it.then after its done see if the drive is dirty again and restart the system to chck if it still chcks for errors.