Did you do a full uninstall of all old drivers when you changed cards? You may have to manually remove stuff from the regisrty to do it properly. (Video control sets need removed, so do the straglers that leaves behind.)

Drivesweeper can remove most issues, read up on it before you run it thou.

http://www.guru3d.com/content-page/guru3d-driver-sweeper.html

Do you have built in video on the motherboard too? And if you do, is that disabled in the bios and excluded in device manager?

Is your motherboard Bios PCIe 2.1 compatable? Some are not.

There are a ton of drivers for it as well. But you should be using this one.

http://support.amd.com/us/gpudownload/fire/Pages/fire_win7-64.aspx

The above driver works fine with V7800 and V8800's.

There are more than a few older versions as well. You may have to experiment to see which one works the best. Just remember to completely uninstall each time.

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