Registry errors from installing and/or removing programs that utilize video codecs.

Here are the latest video drivers: Lets at least make sure this is out of the way. Drivers are usually updated monthly. Try not to use automated programs for updating drivers because sometimes those programs just don't work properly. I don't care who gave it a super great review or how popular it is, this is me talking from experience.

Can you tell us which version of Windows and what your card and processor are?

Below is for ATI Catalyst or Nvidia cards.

ATI for XP
http://www.majorgeeks.com/ATI_Catalyst_Drivers_for_Windows_XP_d4038.html

ATI for Vista or Win 7
http://www.majorgeeks.com/ATI_Catalyst_for_Windows_7Vista_d5503.html

Nvidia for Vista or Win 7
http://www.majorgeeks.com/Nvidia_Forceware_for_Windows_VistaWin_7_d5935.html

Nvidia for XP
http://www.majorgeeks.com/Nvidia_Forceware_for_Windows_XP_d5934.html

Every time there I run into trouble on the road, there is always a dwarf at the bottom of it. Don't they know how to drive above ground?