Often restarting the Pc in safe mode enables you to do this, restart your pc and after the bios has flashed by keep tapping F8 key, then select start in safe mode. The pc witll start in a mode with few drivers etc running. The screen will look a little wierd as it's running is basic graphic settings. After deleting just restart and your Pc will go back as normal. If this don't work post back as there are other avenues to try.