|Your power supply shows two 12Volt rails at 20 Amps BUT then shows a total combined 12 Volt amperage rating of 28Amps so it looks like the manufacturer is using some raz-a-ma-taz with the numbers. Combining this with the 30Amp rating on the 5Volt rail (which will never be used) in order to push up the overall Wattage ratings, which is common on cheap power supplies, makes me suspicious of all of their ratings. While in theory, the graphics card should work on a 500 watt or higher power supply, yours may not be up to the task of running it under load.|
Before assuming that the video card is bad, I would try it with a better power supply, especially if you can borrow one to test it with.
You want a power supply that is 80% or higher certified efficient, has a single 12Volt Rail, Active PFC, is made by a quality name brand, and comes with a 3-5 year warranty.
Look at these:
I have had good results with Corsair and XFX models.
You have to be a little bit crazy to keep you from going insane.