overclock stopped boot but gets through post

I am using an asus p5ne-sli motherboard with a q6600. I have got a scyth infiniti cooler on it, and I managed to overclock the board to 300mhz cpu 9x multiplier without any problems, had it running a week or so and it seemed fine, max temps aroun 69 degrees after half an hour of prime. I was running at 1.4v to core and 2.01 v to 2x 1gb sticks of crucial ballistix 8500. The ballistix is running at 4-4-4-12 which is under the recommended 5-5-5-15, could that also be a problem?

I thought i would try a little more and go for the 333.3 mhz push so I turned up the v core to 1.45v and left the voltage to ram the same however now whenever i switch on i get the post "beep" noise but then it hangs on the p5ne-sli startup screen and goes no further.

How do i reset my bios back to original / get it working again as at the moment it wont boot into windows. Is this something to do with CMOS? could someone give me a quick explanation of what cmos is.

Thanks

When ever you overclock the cpu be sure to set the ram back to stock settings. Continue on the cpu until it you are happy with the overclock or limited by heat/stability etc.

Once the cpu is stable play with the ram settings/timings etc. I wouldn't just keep turning up the vcore on the cpu either before seeing how far the fsb can go. Slowly slowly catchy monkey is the way to go.

Always go up slowly with fsb first until you have stability problems. Then increase the vcore by the smallest increment available making sure that the pc is stable at that vcore and temperature. Just increasing vcore willy nilly is a good way to fry your cpu.

If your cpu is at 70°C under load at 1.4v then that is as high as your cooling is good for imho. You can probably increase fsb a bit more at this voltage. You may want to read Clunk's excellent overclocking guide.

Look in your motherboard manual to see how to reset the cmos. Usually there is a reset switch. The other method is to turn off the pc, remove the battery and switch the jumper to the clear cmos position, leave for 5 mins then put the jumper back to the normal position and insert the battery. Again consult your motherboard manual.

CMOS is a Complementary metal–oxide–semiconductor . This is non-volatile memory that holds user-customizable configuration data (passwords, time, date, hard drive details, etc.) accessed by BIOS code and uses very little power. A small battery powers the CMOS when the PC is turned off. "Reseting" the CMOS sets this data back to the factory defaults.

You usually dont have to remove the battery to reset the cmos, just flick the switch on the mobo (if it has one), or turn it off at the plug and swap the jumper from pins 1+2 to 2+3 for a few seconds, then swap back. Then turn on your pc and setup the bios again.

well i managed to reset it to default by removing the battery. Its working again now. thanks