I am trying to install a Radeon hd 6770 into a older hp of mine , but when the card is installed the fans rev up but the computer won't post. I've tried with a diferent power supply and had the same problum, but I tried putting my Radeon hd 7770 in and the computer posted fine. I also tried putting the 6770 into my own build and it booted just fine. There is no os on the hp yet. Any ideas?