Every time I try to start my computer it starts loading Windows and then reboots. When I start up, everything works perfectly until I get to the "Windows did not shut down correctly last time" screen. I'm given the various choices (start in safe mode, safe mode with networking, last known good config etc...). No matter which option I choose, Windows begins to start up normally, and right when it would usually go to the login screen, everything shuts down and the computer starts rebooting. Please help!