PSU keeps frying in new system

I bought a motherboard combo from www.monarchcomputer.com. It was the ASUS P4C800 Deluxe with a pentium 4 2.4 ghz 800 mhz FSB processor w/heatsink and fan. Imounted the
motherboard in a chieftech aluminum case. I included a floppy drive, a SAMSUNGDVD/CDRW drive, a SEAGATE 80GB Serial ATA Hard Drive 7200/8mb/9.4/S-ATA-150, and a RADEON
9800 Pro. I attached all the peripherals accordingly and carefully. I installed windows xp and my software and games. Everything ran perfectly on the system and the computer really blazed through everything I threw at it. I had the computer on for about 14 hours, and then shut it down for the night. When I went to turn it back on it started but only for about two seconds and then it
died. I tried to boot again but I had to turn off the power supply then on again to find it to doing the same thing; starts for two seconds then dies. I noticed that the green power indicator light on the motherboard comes on when the power supply is connected and all of the fans and the
cathode tube light all turn on. I took the power supply back to the retailer and they told me it had
died. I got a replacement power supply and the same thing happened to me again; the system works fine until I shut it down at which point the power never works again. I replaced the power cord to the power supply and had the broken power supply replaced again but the same thing happened. I have built many computers before but I have never had this happen
and I have no idea what could be causing this problem as it is a brand new system with all new parts and it keeps frying the power supplies. The brand of power supply I have been using is a 450 watt power supply that is the new ATX 12V form factor and is supported by the Pentium
4 requirements. The brand is called realpcpower and can be found at www.realpcpower.com. It has an AC input of 110/220volts~50-60Hz 8.0/4.0A, and DC output of 450 Watts, DC Volts +5V -5V +12V -12V +3.3V +5Vsb
MAX Amps 30A , 0.5A , 18A , 0.8A, 14A, 2A

It's possible that the power supplies are just rated improperly. A lying manufacturer? Can it be?

Have you considered a name brand power supply, like a Fortron, Sparkle Power, Aopen, or Enermax?

<font color=blue>Watts mean squat if you don't have quality!</font color=blue>

*nods*
Judging by what you have written, there are a couple of likely cauzes to your problem.

1. Poor/dirty mains power
2. Defect in the mobo
3. Dodgy PSU.

As the system will RUN its probably not numbers 1 or 2... as they cwould liekly cause random crashes all over the place.
I dont know the brand, but it wouldnt suprise me that its a pretty crappy 450W unit.

If you look at the side of the PSU it should give current Ratings for each of the voltage lines... anything below 25A on the 12V line is just too low IMHO.

A Proper brand name psu is in order. I prefer Enermax.

<b>Melb_angel: PooBaa's <A HREF="http://www.secretarythemovie.com" target="_new">Secretary!</A></b>

Thanks guys! I get paid tommorow so I am going to go ahead and invest in a brand name power supply. Which one is going to be the best for my needs without eating my wallet?