I installed windows 7 as my main os. then i unsintalled and reinstalled vista but now im trying to go back to windows 7. I ran the reformat everything worked fine and it rebooted. It shows the starting windows screen then goes to a black screen that says windows 7 for testing purposes only. It will not reach the starting windows for the first time screen. ive tried doing this 3 times now so i dont know what to do.