comp powers down on its own

I recently put together a computer and shortly after it boots it shuts down on its own. Any ideas?? Thanks.
here are specs
Motherboard- S-series GA-945GM-s2
CPU- INTEL|CORE 2 E6400 2.13G 775 R
video card- PCI express ATI X1800XT 256MB 100-435840 R
RAM- 1Gx2|MUSHKIN DII667 991503 R
HDD- 80G SATA
Power Supply- 500watt
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What kind of case did you put it in? You may have a bad switch. Is the memory seated properly? How far does the computer boot? Does it post? Does it boot to desktop?

 

it POSTs, and I am trying to install windows xp pro. it goes from 5-10 mins fine then it just shuts off as if someone has pulled the plug.

 

Do you have another power supply to test with? I have never had a processer shut down so i dont know if it completly shuts down. ed

 

It might sound silly, but is the CPU fan running? Could be overheating.

 

yes its running although it may be over heating. But I have a few fans going.

 

if the processor itself is shutting down, would that cause all the power to fail. The power supply is good also.

 

Thats what im not sure about, have you had the heatsink off since the build, if the heatsink is not seated on the cpu, they will throttle back and shut down,but im not sure about losing all power, i would reseat the heatsink, i think thats whats going on. ed

 

I will try that right now and let you know shortly. Thanks.

 

I had a similar problem once and it turned out to be a bad stick of RAM. You might also try using only stick of RAM at a time and see if it continues.

 

seems to be workin fine now. Thanks a lot for the help ed.... again.

 

No problem, glad you got it going. ed