Windows 7 won't boot when graphics drivers are installed

I'm not really computer-savvy so you'll have to bear with me. Over the past couple weeks I've had some minor problems when running games. I have two AMD Radeon HD 6850 with crossfire, btw. After coming back home one day, I noticed that my computer would always freeze at the Windows logo when I tried to start it up.

After reading around online, I started it in safe mode and then rolled back the drivers on the graphics cards. After this I was able to boot Windows normally with no problems. However, any time I try to re-install drivers (even older versions that used to work for me) the same problems happen when I try to boot.

I've already tried uninstalling everything and using Driver Cleaner, but the problems still persist. If there's any other information you need, let me now.