it sounds like your psu is fine. if the fans spin for a second then it's working, something else is making it shut off. is there a lit LED light anywhere on your mobo, it should be on if it's working and power is connected to it. If you see the led then your problem is probably not the psu or the mobo, but i can't be sure because they never really tell you what the little light means and it could be different for different mobos
Intel P4 530 @3.15 Ghz, ASUS P5GDC-V Deluxe, Barracuda 200GB SATA HD,500 Watt Glacier Power Supply, ATI Radeon X800 XT PCI-e,1.553 GB PC3200 DDR400 RAM, tv out: 27" flat screen,optical out: 500 watt 5.1 surround, 3dmark03:11551, top fps:1200+ chit-chigity check yo self before you wreck yo self, cuz shotgun bullets are bad for ya health.