This one is for any hardware gurus....
This is not strictly a Linux issue, however, here goes.

I just rebuilt my system to the following

AMD Athlon 64 3200+ Socket939
Abit KN8V1.1
Innovision GeForce 6600GT PCI Express
Seagate Sata 120GB
Lite On DVD Combo Drive
3 X 512MB Kingmax DDR400 PC3200 Ram
iCute 0408SL Case with 500W iCute PSU (18A on 12V Rail)
fdd unknown brand

This is my fourth rebuild and the first time I have had an issue. What happens is the following:

Connect power, red light on Motherboard comes on, hit power button and the system powers up, All case fans start running, CPU Fan starts running, Northbridge fan and GPU fan all start running, green power led comes on, all looks good. Get what sounds like the successful POST beep then system shuts down to only the red light on the motherboard.

So, started by disconnecting all drives and two of the Ram sticks and trying again. Same result. Disconnected all case accessories Front Panel audio, usb and Firewire, and case fans. Tried again, same result. Tried different power supply (400W PSU) same result. Removed Graphics card and reseated, same result. Removed memory and reseated, same result. Tried other memory same result. Removed memory altogether and got the standard continuous beeps from POST, indicating no Memory. This was good, not a Memory issue. Removed the case reset switch, HLED, PLED and speaker. No beep but still shutdown. Reconnected speaker. Removed Graphics card and still the same result.

OK, I haven't removed the CPU as I couldn't take it off without removing the heatsink and fan assembly. Also, I haven't tried different Graphics cards or Motherboard as I don't have spares (not S939 or PCIX GPUs) but I am going to try and arrange to check these on the weekend.

I have had all these components operational before just not in this configuration. They are all compatible as the only really new things are one Memory stick, the PSU and Case, all the rest of it comprised my last machine (with some other bits and pieces). The case and Power supply are powering the machine I am writing this thread on.

If any one has any ideas I would greatly appreciate them.

Thank You

Might be a CPU over heating problem. I've seen that happen with no warnings given. See if the fan heat sink is actually making proper contact with the CPU. If not, that will cause a shutdown...

I agreed with ezrider. I would removed the heatsink and apply some cpu coolant then give it a try. Make sure the heatsink is all the way down and touching the CPU. If this doesn't fix your problem. It could be your power supply just not providing enough juice for the system. You might want to try a better power supply. Abit motherboard with a powerful video card will required a name brand Power supply.

Things I'd suggest checking:

1. BIOS -- get into BIOS and walk through all settings to confirm that they're appropriate. You definitely want to verify that the system recognizes your equipment correctly, in particular the hard drive, RAM, and CPU

2. Assuming your boot sequence lists your CD ahead of the hard drive, use a Live CD such as Knoppix to see if you can boot from it. If so, then your hard drive could be the problem, and may not be jumpered correctly, connected correctly, etc.

3. I'd also agree that you should check the CPU. Overheating is a possibility but I don't think the CPU would auto-shutdown after only a couple of seconds.

4. Assuming all the components are new, it could be that you just got stuck with a lemon. This is not very likely, but if you have exhausted every other possibility, you may have a bum mobo or CPU.

Good luck with it either way

Thanks for the suggestions, it is looking like a CPU overheating problem.

I have ruled out power supply as I had this board, chip and graphics card running off a 350W no name power supply for about 3 months, with a heap of fans and neons as well.

Unfortunately, I can't get into Bios. It shuts down less than one second after POST. It doesn't even have a chance to put a message on the screen. I suspected the video card because of this but even without the card I have the same issue.

This weekend I'll be able to check it.

Thanks for the feedback.