you could try putting your vista disc in dvd rom
let it load up & when it opens up, it will give you an option of repairing your operating system. or you could try in safe mode, when you get to your desktop click start/run/in the run line type "cmd" without the "
when on command prompt type "chkdsk/f" without the " the /f parameter is for fix. goodluck
gary
March 2008