black screen startup

OK - I've been waiting for ever to participate in the CPP, and now that it has come - it doesn't work. I have seen PLENTY of posts - but nothing helpful. Would appreciate help with this issue AS SOON AS POSSIBLE! Here's what's happening: - Installed Windows Vista Beta 2 as upgrade over Windows XP MCE (Media Center) - Completed install and restarted computer, but computer only loaded Windows Boot Manager. - Tried all possible options (i.e. Earlier Version of Windows, Microsoft Windows, etc.) and all bring me to a black screen with "Windows Vista Beta 2, Evaluation Copy Build 5384" in bottom right hand corner of the screen. This is driving me crazy because I want to try Vista SO SO SO bad. Brand new video card (brand new computer) and no good resolutions on discussion boards.
ANY HELP GREATLY APPRECIATED!