Thought I was fairly clever, but I cannot figure this out. I have 2 PCs each running a Sapphire brand HD5770 1GB video card, though 1 card is about 8 months newer than the other. I was using it on my #1 pc (was on quad 9400, then I upgraded to an i7) and the older one on #2 pc (quad 6600) Both working without any problems. Am running a legit copy of Windows 7 Pro SP1. Bought a new 6950 card for my new i7 and decided to sell one of my 5770s. So I thought I'd put the newer card in my Q6600 and sell the older card. Did the swap and all seemed OK. Booted up, into Windows (I heard the sound card "kick in" with speaker noise), then the login screen appeared. Entered my password and Windows desktop then appeared (though at 800 x 600 as I guess the pc detected the different serial - or bios - or whatever) I changed the resolution to my normal setting (1600 x 1050) still OK and didn't seek reboot. Windows then did a self update to install the drivers for the new card. Ran the Windows assessment tool again (as it was greyed out with the old results). Windows then said it couldn't finish the assessment, so I figured it needed the reboot after all. Rebooted the pc, all seemed OK - DOS & post messages as normal, then the starting windows screen, then heard the speakers cut in (obviously the sound card being enabled) then I heard the "Windows' start sound and then the login screen appeared, as normal. Entered my password then the screen went black with only the arrow head cursor of the mouse visible. I was able to move the mouse as evidenced by the moving cursor, but unable to do anything else. Hit the reboot button, and selected a safe mode start. The normal sequence of events followed, the login screen appeared normally, though at 1200 x 800, I entered my password and Windows went into safe mode. Everything worked OK but as it was in safe mode, of course I wasn't able to change any settings. Then I thought maybe it was a problem with selecting the wrong monitor (wasn't that a clever idea). I shut down the pc, changed the VGA cord to the other outlet, restarted normally and the same thing happened again - black screen after the login with only the mouse cursor viewable. Can't see how it is a problem with the video card itself (it works in DOS and shows Windows start sequence and login screen - so what could be the cause of this drama? Any advice will be greatly appreciated!!!!