|Has that ever worked properly?|
Have you installed or re-installed your video software, or have you loaded different video drivers than you were using before, since that last worked properly ?
Have you re-loaded Windows since that last worked properly ?
Is your bios Setup set correctly for your type of video adapter ?
Intialize video first, or Primary Video, or similar, should be set to the type of video adapter you are using -if that's set wrong you still have video in Windows but the specific drivers loaded for it Windows will not work properly in some situations.