I have an HP Pavilion series P7-1054 AMD Athlon II 645 Quad Pro Processor 6GB Ram and was using the original graphics card which was part of the motherboard. Now I have an Asus HD 5450 1GB DDR, however this PC comes with a 250w power supply and when I installed the card, the computer won't start up. I changed the power supply to a 700w I had spare in the house and now the fans on the power won't work. I am wondering if I messed something up or if its the power supply all together. Do I need to get a 500w maybe? Not sure what the problem is. Also I had the HDMI cord connected directly from the new card to the monitor and the monitor would try to turn on and go to sleep mode. So I put the cord back to the VGA and it worked fine. Not sure why it won't take the HDMI. Can you help?