Update.... eventually I bought an NVIDIA Gigabyte Geforce GTX650 OC 2GB and 600W PSU. The PSU Installed fine but the GPU was a disaster. I tried everything over two week period....installed it 20 times, installed drivers from Gigabyte, from Nvidia, unstalled onboard graphics, restored PC, contacted Nvidia/Gigabyte/HP, booted Safe Mode then installed...no one could help. I did see the card 3 times but it reverted back to the onboard graphics, and then in the end I uninstalled the onboard and it just stopped working unless I put back the original Radeon card (Note that there is no option on the P6 to override the Onboard graphics in the BIOS, which seems to be a fundamental flaw). I live in HK where there is no return policy so I'm resigned to selling for half price. I'm not prepared to by a Radeon to see if that works instead. So I will be buying him BF4 for his PS3 instead (which is a shame as they are region specific and all the kids in HK play on PC. All I can suggest is you try a Radeon. Let me know how it goes.