xfx 8300 motherboard turns off

Hi All
I need help please

(I have lodged this as a ticket)

my PC keeps turning off. It turns off JUST as the "windows c" appears with the green bar underneath.

specs:
windows Vista 64 bit
xfx geforce 8300 AMD socket 940 DDR2 mobo
Phenome quad core 2.4 Ghz
9800 gtx+ GPU
700w thermaltake toughpower
2x 250 gig seagate HDD in raid 0 (SATA)
8 gigs ram Transcend (4x2G 800 Dimm cl5)

CPU temp sits between 45 and 47 C / 116 F
CPU voltage 1.2V +/- 0.02
SYS Temp sits at 37 C / 98 F
DRAM voltage 1.9V

I loaded an application (DSTv drifta) and activated a game (BC2 vietnam) the day before.

I have cleaned heatsinks, put fresh silver paste and blown mobo with clean air taking care not to spin fans.
I have changed ram around, reseated it, put in one unit, two units, 2 different units.
I have swopped the Power supply with one that WAS working in that same machine.
I have completely removed GPU and alternatley disabled on board GPU (iGPU)
I have reset bios/cmos and played with APM and ACPI (disabling them/support for them in bios)


I put both a vista and 7 disk in dvd rom and when vista reaches the end of the white 'loading windows' bar
across the screen it turns off, and when 7 gets to the 4 balls coming together (once or twice it got to the
windows flag logo) it turns off.

I disconected the HDDs and tried an IDE and another SATA drive before and with the windows install disks.
I have disconnected EVERYTHING, removed mobo and checked pots and reseated and reconnected everything.

now, if i try boot off HDDs it says missing operating system (I am assuming thats because of resetting bios
and hope i dont have a HDD problem as well - remember i was in raid 0)

A friend helped me get a linux boot disk (ultimate boot CD - ubcd503.iso) and i get to the options page,
for a few seconds or until i press a key. What seems to happen, if i do a cold start, i get to press
a few keys to see the options before it turns off, but whenever i restart, as soon as i press a key it turns off. no matter what key.

what i havent done yet:
I havent checked silver paste on north bridge yet
havent replaced CPU
havent taken a 10 pound hammer to pc

OH - some more info - in the post it used to show the raid drives - but doesnt anymore. does anyone have any ides please.

if your idling at 45-47 it sounds as if you are having a thermal shutdown

thanks for responding Stang. :)
if the fan is working and new thermal paste in place, then is the cpu toasted or would it be other chips on the mobo? :shrug:

which amd phenom is this? the original or phenom II?

Could be bad caps, are any of the capacitors leaking or bulging at the tops?