My Windows 7 computer was working fine when I shut it down last night but now will not boot up. When I started it up, it made it to the windows log in screen but froze when I put in a user account password and hit enter. Since then, it only gets to where it should say Welcome to Windows but just sits there at a black screen. I've used my cd and rand the auto start up repair but after it runs and says to restart the computer, the same thing happens. If I hit the f8 key to try to boot to safe mode, I just get the black screen. What do I try next? Thank you.