Ok, so I got a Mac Pro I believe it's a 2007 model or some where along those lines, it's 2.63 ghz quad core. None the less here is what happened. Came home one day to find my USB not working at all it would charge but not connect to the computer. So I reboot still not working. I turn it off and take a look inside nothing, reseat the ram just to be sure. Ok, turn it on, nothing happens, no screen I hear the fans spinning and the hd spinning. Hmm odd. So I take out each card and try one by one to see if any one them are causing a problem nope. As a side note the computer light comes on, but if I like the power button it just shuts right off. Also the computer power up when I put the plug in the back without pressing the on button. today i took the computer apart to see if I could find any blown caps... hmm nope. Went to the local computer store but they don't test for anything mac so he said I could try out their power tester nothing would light up on the tester but it may have been wrong pins. CD drive showed all voltages but 3.3v. Now im not sure if it's the MOBO or the Power supply is there any way to test this out? or if I toast something else? I have no clue. Chris ps. if I plug usb in while it's on I can charge my iphone.