So I've installed a new HD 6770, it's in good condition and appears to be running great. It's booting with the PC and all of the usual stuff is there. Desktop, Internet, etc... all good. However, I've tried to play Battlefield: Bad Company 2 and it's acting strange, it loads fine and I can enter games but I get random frame stutters, small parts of models are also disappearing and the game has frozen.
I also tried a much older game, the first release of Call of Duty and I get ridiculous frame rate issues.
UPDATE: Apologies for the unneeded post. I figured my problem out.. At least, I think I have. I just cleaned out my PC and re-seated the card and reinstalled my drivers. It seems to be running a lot better. Sorry once again.