I had put my computer on standby for a minute but when I went to turn it back on the computer had shut off and when I tried to turn back on nothing happened. I opened the case and everything was connected and I could see little green light showing that I have the psu switched on lit. Do I need a new psu? Or could be that there is something wrong with the motherboard? I'm using my sister's computer at the moment. I have an Antec Sonata II case w/ 450w psu that came with it and my mobo. is an ASUS A8N-E.