Try starting up in Safe Mode, which is a diagnostic mode that only loads the basic Windows drivers and options, so that you can troubleshoot issues like yours.
To enter safe mode, start tapping the F8 key at the top of your keyboard as soon as you startup your computer. Do this until the Windows Startup Menu appears and then select Safe Mode from the options.
Once in Safe Mode, go to Start Button-> Run and type CHKDSK /F and press the Enter Key. You may get a warning that the computer will check the drive the necxt time the computer starts up. If you do, just answer Y