System powers on, nothing else

[AdamantC]

Specs: WinXP SP3, Athlon 64 5200+, Gigabyte GA-MA770-UD3, Corsair XMS DDR2 1GBx2, two WD SE16 320GB HDDs, HT Omega Striker sound, Asus 8400GS, Ultra 550w PSU.

As the title says, it will power on but that's it. No BIOS splash or POST. I've pulled the entire system apart checking for any signs of whiskering, scorching, or bulging caps. I've tested it with only the CPU, graphics and with one stick of RAM at a time. Tried a different PSU. Also popped the BIOS battery out (for several minutes) and tried plugging in the system speaker to see if the mobo would spit out any error beeps, all to no avail.

Also note it just died with no prior indicators what so ever.

The only thing I can think of is the mobo or CPU crapped out. Any advice would be much appreciated.

Edit: Forgot to mention that the power and reset buttons do not work after the system is powered on.

 

[Motorheader]

With everything you described you have done as far as issues and troubleshooting I would say motherboard. Those Athlon processors are pretty hardy and unless you had some crazy overclock going that went awry it's not likely the processor. I've never encountered one that failed running normal specs.

 

[AdamantC]

Thanks!

Everything is stock as it is a general use system. Generally the heaviest load it sees is Youtube.