Well, you pulled the battery should have reset the bios to defaults. Leave it out for 10-15 minutes cnext time to absoluty sure and unplug the system too. Find the CMOS clearing pins/pads in order to use them as a last resort. If the problem persists, yeah it maybe your mtrbd. but the cpu could have fried. This is the result of OC'ing as may have noticed. Try the above and see if it can come alive, another cpu or test it elsewhere. You can also check the mtbd. for blown caps or bludging ones as that can happen from a known problem 18-24mos. ago of weak caps.
good luck -----Willy
Well Ive been playing with my computer lately and used some of that silver thermal compound of my processor fan... made it run alot cooler.. so I decided to bump up the speeds a bit.. however when I put it up to 166 in the bios the monitor turned off right after reboot and it hasn't came back on since.. all the fans are running including the one on the video card itself.. it was working fine seconds before running at about 35 degrees C... Ive pulled the battery and that didn't help any..
oh also I pulled my motherboard last night so I had to unplug/replug everything.. and when I boot the computer up now after the lil bump up there isn't a beep sound like usual...
I built this computer myself about 2 years ago, and its had a couple problems but nothing major.. haven't had to replace anything as of yet... thanks alot
Update: Ive checked the ram/hard drive/video card and cleared the CMOS, right after that its doing this revving thing when I try to power on.. its like intermittent power.. so I tried to hook up another powersupply and it does the exact same thing... is it my motherboard?

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