Cooler Master "Shutdown"

The problem, the computer is experiencing a “shutdown”, it
starts up, everything is getting power sometimes I get as far as a
"splash" screen then it goes BLACK power ceases. I’ve started with
the case’s “Power Switch” Button on top of the case, by the way the
LED stopped functioning. First by, unplugging it from the MB and crossing the 2 pins with a
screwdriver to boot the machine, it shuts down. 2ndly I purchased
another Power Supply and installed it to have the same occur –
shutdown - should I assume at this point that I have a bad
Motherboard? How do I “isolate" the MB for testing? The “system” was
not built by me but my “Father-in-Law” who is now deceased, I was
given the machine and have been using without incident for over a
month until now... A little more background about the “build” the machine
had Windows XP Pro SP2 installed and I erased the HD and installed
UBUNTU Linux 8.10 without issues. I’ve read that a driver/ or the
lack of, could have caused this but I didn’t see any sort of failure
until now. I’ve detached the HD to but from a CD it won’t. The
machine was built in Nov, 2006 from Components purchased thru
NewEgg.com and are the following:

CoolerMaster Centurion 532 Case
Gigabyte GA-965P-DS3 (Rev.1) Motherboard
Enermax EG565P-VE 535W Power Supply
Intel C2D E6400 2.13Gig 775 2M Processor
Corsair 1Gx2 240P twin2x2048-6400C4 Memory
Sapphire/Radeon 1950X DualDVI VideoCard
Seagate SATA 320Gig ST3320620AS – OEM Hard drive
Lite-On SHM-165H6S DVD Burner

I have written to Gigabyte Technologies about the MB, I await some
sort of response, I guess I’ll try some “forums” to see whats up …
any insights you may have would be appreciated. Regards, PLM