Also if you've moved from Nvidia to AMD make sure to uninstall Nvidia drivers......Win 7 and Win 8 normally handle them fine as seperate items; but once in awhile things can go screwy. Its no where near as ugly as it used to be with XP.
If you're having issues; you can always give me a pm and I'll see what I can do to help.
Few things; you getting video out of the card? Everything fully seated? external cables plugged in if needed?
Two: AMD's drivers are fine and have been for a long time. You get good and bad just like Nvidia's drivers and those that keep trying to say AMD's drivers are bad; are either a fan boy or someone with an agenda......
I've ran both; gotten issues with both.....solved 99% of issues with both