Hey guys, was going to buy a new cpu anyway so figured I'd see if I could get my core 2 duo E7500 to 4.0ghz (which I was not successful obviously.)
I checked the specs for the mobo (EVGA 750i) and the processor and didn't exceed their maximums. I put the FSB to 1300 (roughly 3.6 ghz, which would lockup after any kind of load.) Moved the voltage up bit by bit and took the FSB voltage to 1.35 (which the mobo is capable, and is very near the max end of intel's recommendations.) It hung on bios the first time, restarted and immediately set all settings back to factory (1.29v if memory serves and 1100ishMhz fsb) and it goes to the pre-startup "run windows start up repair." I select it, it says loading files and then goes back to the "run windows star up repair" selection screen. If I select run windows normally it goes into the loading screen (http://www.bokeboke.co.uk/data/blogimg/200901111505_01_...) but it doesn't animate the windows logo, it just has the text and then restarts to BIOS.
I examined the chip and mobo, no smells, no rainbowing..I'm lost.
Also the RAM's bus was increased to ~940mhz (factory 800)
Also, I don't have a second box to interchange the parts to see which one it is..hooray for planning.
Next stop should be a guide for your particular motherboard. Google is your friend.
You can also look for 680i overclocking guides. The 750i is an upgraded 600i chipset that is compatible with the 45 nm C2Q CPU chips.
The reason your overclock is failing is because of your RAM settings. At a RAM clock of 940 MHz, you are trying to make the RAM run faster than it can. Reset the RAM timing to "linked". At this point, the FSB frequency will be 266 MHz, the FSB clock will be 1066 MHz (quad pumped bus - each bus cycle will generate 4 bus clocks), and the RAM clock will be 533 MHz (DDR2 RAM, remember?).
If you still have problems after this, you should repost in the Overclocking Forum.
another thing to consider is that you may have left the RAM voltages at stock while trying to OC it to 940... You could have bumped it from say 1.8v to 1.9 or 2.0v (never go above 2.0 unless it is supported by the RAM manufacturer.