4Ghz??? You realise that that's twice the standard clock? Good luck :rolleyes:
I thought you said you were sensible now? Having a bet over how high you can clock your CPU before it goes pop is just plain stupidity. Find a reasonable clock (52 degrees at load isn't worryingly high, but clearly not advisable. My 3Ghz quad runs at ~40 degrees at full tilt, and it's on air cooling, so I can run it at that all day without worrying. The max temperature your CPU will do, according to Intel, is 73.2 degrees. You're cutting it a little too close for everyday use).
You've just said it was unstable after 10 seconds on 3.4Ghz, sheer logic would suggest "Hey, let's not try and increase it even higher!". How much machinery do you have to go through before you can realise not to cock about with it? Can you just send them (or even better, the cash) to me instead of frying them?