machine rebooting at POST - help!

so it's probably my fault... I had my machine overclocked the other day at 3 ghz and the temps were quite high. it BSOD'd whilst playing a bit of battlefield 2. in fact it BSOD'd the previous night too. and also crashed without creating a dump file. anyhoo, i tried to switch it on last night and it reboots before it displays the whole of the memory count. i've got 2 gigs and the memory display said 20 instead of 2097152. resetting the bios gave me the bios recovery menu, choosing defaults and the same old reboot on POST

i did actually try putting the ram in the other slots and using 2 other sticks - made no difference

any suggestions what could be at fault

my system is as follows:
gigabyte eg41mf 2s
pentium 2160
2 gigs corsair xms2 ddr2 675mhz
corsair 520hx psu
sapphire ati 1950 pro
couple of hdds

I would have said start by downloading memtest 86+ (obviously on another machine :) ) - burn it to CD and try booting off that - but if you have tried different memory sticks, that would tend to suggest it isn't memory.

If you have reset the bios to default and it still isn't working, it tends to suggest a fault with the mobo (based on what you have said here). As a last resort, it might be worth clearing the bios configuration stored in the CMOS. The instructions will be in your mobo manual, but generally removing the battery back up (often a small flat 'coin' cell) for about 5 minutes, then replacing it.

Yeah, remove the CMOS would be my second thought. Firstly, just disconnect the entire PC from mains power for 10 minutes, just let the whole thing rest and then try again.

I found I used to get in reboot issues at POST and all it took to fix was taking away mains power for a bit.

thanks for the suggestions guys - i figured it out though.
i have a wolfking keyboard attached to my monitor. disconnecting the monitor usb sorted it. the wolfking plugged into the base unit was fine, other devices plugged into the monitor were fine. all a bit strange really. thank goodness it wasn't anything more serious though!

Glad it's sorted. Not the first time I have heard of problems with USB - possibly because the USB hub in the monitor isn't recognised. Still, job done!