Problem with an overclock

Setup:

- Intel E6750 Core2 Duo (2.66 GHz) [Used stock heatsink and fan with some Zalman thermal paste]
- XFX nForce 680i LT SLI motherboard
- 2 × 1GB Platinum OZC RAM
- Inno 3D 512MB 8800GT
- Hiper SLI ready 650W power supply
- Windows XP (32-bit)

I installed all these components into a case last weekend. Everything was going fine and I was quite happy. I then tried an overclock, but was perhaps a little impetuous and I believe I have screwed up and need some troubleshooting advice.

What I wanted to do was try overclocking the processor, as I believe it to be one that can take a bit of stick. To overclock the processor I went into the BIOS and unlinked the RAM bus speed from the FSB. Took the FSB up to 1400MHz (up from 1333MHz), CPU at 2.8GHz with multiplier at 8x. Managed to boot into Windows XP quite happily for a couple of days. CPU-Z and nTune software showed the CPU clock as being 2.8GHz, FSB at 1400MHz, RAM at 800MHz. I played UT 2004 on top settings to check the stability and system temperatures - everything seemed fine. Compared to the system when it was at its default clock settings, the CPU ran approximately 4/5 degrees C hotter, to about 58 degrees. I checked the CPU voltage with nView system monitor and found the core voltage was at 1.41V - up from 1.3V. I didn't check what voltages were applied to the FSB, but the CPU voltage was increased automatically - I suspect the FSB voltage was also increased automatically by the system but I'm not sure.

Yesterday evening I started to encounter some problems. Sometimes the system wouldn't post anything at all (the graphics card usually posts a screen before the general system check), sometimes the post wouldn't get as far as a RAM check, sometimes it would detect everything fine including all IDE/SATA drives then pause with a message similar to: "System is now in Safe Mode! Reset CPU and Memory frequency in Setup." I enter the BIOS and can sometimes change the clock speeds, other times the system hangs on the BIOS screen (I can't even turn on/off the Num Lock). Occassionally the system starts up into Windows and works fine for a little while, then I get a blue screen of death. Unfortunately the computer restarts instantly so I get all of a second to read the text before its gone - so I don't know exactly what it says.

As soon as I got problems booting, and as soon as I could make it back into the BIOS successfully, I changed all the settings back to their default factory settings. However, I'm still having some problems booting - sometimes it posts nothing, sometimes it gets as far as detecting a processor but fails to go any further like performing a memory check, sometimes it boots into windows and then crashes and restarts.

Does anyone have any ideas as to what I've done? Have I damaged a component - the CPU, the motherboard? If the problem is not with the hardware, is there anything I can do to make the system stable again?

Any help, comments or advice would be greatly received.

OK, well, I've fixed my problem.

I didn't know that the OCZ RAM needed 2-2.2V and the motherboard didn't automatically adjust the voltage. Changing the Vdimm to 2.1V has solved the problem.