Blown CPU?

[nunads]

Greets all...
My sister and I are trying to fix mom's computer ...

Here's the repair history:
1. computer doesn't power on so something got fried, not sure what
2. so sister bought a new PSU and installed it; result: computer still didn't power on
- sis took mom's old PSU and installed it into her computer, old PSU works okay!
3. bought a new mobo and I installed it; computer starts up and I am able to get to BIOS then machines shutdown by itself after ~15 seconds everytime
4. to eliminate possibility of shorts, I disconnected everything from mobo except 24pin main power and atx12v 4pin cables, 1 stick of RAM, monitor and keyboard. Placed mobo on cardboard and I shorted the power switch to power up the computer; result: same, shutdown after ~15 seconds

--- Old Hardware ---
CPU: Intel Pentinum D (LGA 775)
RAM: 2GBx2 DDR2 800Mhz
CPU Fan/Heatsink needs more thermal grease but it doesn't comp doesn't get chance to overheat
--- New hardware ---
Motherboard: Gigabyte G41M-ES2H, http://www.gigabyte.us/Products/Motherboard/Products_Overview.aspx?ProductID=3119
PSU: Rosewill 530W, http://www.rosewill.com/products/1218/productDetail.htm

What do you think could wrong in this scenario? Did the CPU get fried as well as the old motherboard?

Thanks guys for taking the time, much appreciated!

 

[lumpy]

Needs more Thermal grease?...not good,do it right or not at all.
IMO..bad cpu?...short in case/switch wiring?....case to M/B short?....RAM?
Have you tried setting up outsde of case?
What exactly happend?

 

[treefrog07]

That Pentium D will shut down in 15 secs, if the cooling is not sufficient. If nothing has ever been done to the board, get a new CPU heatsink and fan, install it and try again. I use Arctic Cooling Freezer 7 Pro on my 775s. Since it doesn't sound like your mom is overclocking, you could find a cheaper one. Make sure the "thermal grease" is present on the new heatsink - if not, you'll need some to provide adequate heat transfer from the cpu to the heatsink.

If you replace the HSF, and still no start, you may have to get another CPU.

 

[jsc]

Our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-posting-boot-problems

 

[nunads]

Thanks guys, sorry I didn't see the standard checklist.
I'm surprised the system can react so quickly to insufficient CPU cooling.
I'll try what you said.

 

[nunads]

Update:
I installed a new heatsink + fan combo on the CPU and SUCCESS!
The computer works as expected. My mom is very pleased ...
Only thing that sucks is now my sister has to reinstall Windows & apps all over again, since the original motherboard was discontinued and had to install a different one.

Thanks again guys!

 

[treefrog07]

There's nothing better than keeping your mom happy! Have you sister copy all your mom's file to another HDD (hers or yours) for example, so she put them back on mom's HDD after OS re-installation