also try loading in safety mode by after the BIOS screen and before the windows loading screen repeatedly tapping F8 on the keyboard until you get a boot option screen. if it loads in safety mode then you could have a virus problem.
also when you say it all goes black most monitors come up 'no signal' but if its black and not saying that it could be that the registry key to boot explorer.exe has been removed, try Ctrl+Alt+Del and then going 'file' 'new task' and typing 'explorer.exe'
david656
June 2009