Interesting Situation CPU - Need Help!

Hi my name is Ricardo, I'm from Brazil, I'm with a Interesting situation here:
I have the follow pc:
Intel Core 2 Duo E6600 2.4 Ghz
ASUS P5W DH DELUXE/WIFI-AP LGA 775 Intel 975X ATX
2 Gb Ram Kingstom DDR2 PC667
2x 320 Gb Seagate SATAII
ATI Radeon X1950 PRO 256 mb DDR3

And I buy a
Motherboard Intel DQ965GF executive series
Processor Intel Core 2 Duo E6750 2.6 Ghz
Memory 1Ghz Corsair DDR2 PC800

The thing is: my new pc don't start up so I made a few test and the interesting is this:
if I switch the processor the PC works.

I put the core2duo e6600 in the Intel motherboard and the e6750 in the Asus board, the pc turn on ok

the Intel DQ965GF I already make a upgrade of the last BIOS available
and I use 3 differents power supply in the Intel motherboard, switch the memories, all this.

the Intel motherboard only turn on, with the e6600

the question is, by default in theory the Intel motherboard was able to support a Intel Quad Core, if I put a Celeron, Pentium D or at the Maximum a Core 2 Duo E6600 the PC turn on Ok run windows, but if I put a Core 2 duo E6750 and above processor, don't run. Why?

Thanks

I always read the forum and I think this is one's of the best forums have about computer.

Thank you very much

Wow thanks, the most obvious I didn't see.
Thank you very much for the quick response! =)

Yes, that is very dangerous voltage.

See if you can change the voltage setting in the motherboard to a FIXED value instead of "Auto".

Something about 1.35 volts should be fine.

It will likely run lower, but 1.35 is not too terribly high and is definitely plenty of power.

If that works, you could look at lowering the value to something like 1.3 and then 1.25v to see if you stay stable.