Restart your pc and hit CTRL when it changes to the second page in POST. It will then give you a few start choices. Select to start in 'Safe Mode'. Then run Scandisk(prob take about 3-5Hrs if 'Through' is selected and you got 30+gig disk.When its run its course then do defrag. Remember to not touch mouse or run other programs in either task as it can cause freezes. Good luck.