if you are able to load normally after this, the check your video card drivers and/or check the video card itself if it's dusty and all, if so, then clean the slot which it's inserted into and the card itself if not lazy enough....
check your RAM (memtest) and also clean them if they're dusty, as well as the slots they inserted into.
if you are unable to load normally after this then I donno what to suggest, don't know your situation, though preferable would be checking if you're able to start up with another video card/ram.
hope it helps somehow....