problems with intel upgrade can anyone help?

So here is the deal. I just purchased an Intel 3.2Ghz 775 with an ECS 915-A Motherboard. I noticted the motherboard has a 24 pin ATX connector. I first tried a 350 Watt Enermax powersupply. System turns on for about 10 seconds detects processor and memory and then shuts down. The manual stated it reccomends a 24 pin ATX powersupply. however compatible with a 20 pin but the powersupply might not be able to handle load. I then swapped it out with my 480 Watt Antec power supply that powers my FX system. Same thing boots up for a about ten seconds and then shuts down. After reading a review at Hexus they it stated that you can use a 20 pin powersupply that the other 4 pins were really just to handle the load of a PCI Express Card. I have even tried to boot the system with just the video (AGP) Memory keyboard and mouse plugged in and still no joy. If anyone has had this issue or knows what's going on I would appreciate the help tks.