I've just got a new Sapphire Radeon 5450 512Mb DDR3 which i inserted into my PC. However when it is inserted the computer will fail to load anything. It turns on and the fans go to max but the bios doesn't load. I have a HP DX2250 with a 250W PSU but i tried it on an Acer desktop with a 250W PSU and it ran and installed perfectly. The Acer is running Vista and the HP is running Ubuntu 11.10, would that cause it?