system wont POST unless I clear CMOS
 

I bought a used mobo/cpu combo (Asus P4b266 with a P4 2.6 ghz) from a guy I work with (who built this sytem I'm on now, as well as the systems of several other guys at work). I was assured that it had been tested and was able POST with no trouble. I bought it with the intention of building a more powerful system so I can give this one to my daughter. After installing it into a new case with new powersupply and new hard drive and 2gb of new RAM, I can only get it to POST if I remove the battery and clear the CMOS. If I make ANY changes whatsoever in the BIOS, it refuses to POST. Not only that, but it wont even let me get back into the BIOS until I clear the CMOS. If I attempt to let it boot without making BIOS changes, it hangs after successfully updating the ESCD.

I've been through the entire manual for the mobo (all 140 pages of it) several times, checking and rechecking connections and jumpers (just about everything is set to default) as well as BIOS settings that might be causing conflicts, and am fairly certain I havent boogered anything up.

I think the BIOS is screwed up in some way. What do you think?

note: the POST (when I can get one) shows that the RAM sticks are good (as does hardware monitoring in the BIOS, which also reports that the processor is ok.) system is not overclocked. barebones install (HDD, DVD drive, AGP graphics card and NIC)

edit2: after spending a couple hours searching tech forums, I got a few ideas to try:
replace the battery with a new one - no change
pull EVERYTHING not absolutely necessary - pulled NIC and 1 stick of RAM (out of 2) - no change
disable anything not absolutely necessary - no change
pull my already thinning hair out and scream at it - no change

aww cmon...does NO ONE even have the slightest idea?

Check the mobo carefully. Are there any capacitors that appear puffy or may be leaking?

Try leaving a bootable CD in the optical drive. Some BIOSes behave in a weird manner if there isn't at least one bootable component on the computer.

You aren't trying to overclock it are you?
If you haven't done anything out of the ordinary to it you could try changing the parts with equivalent ones if you have them, sometimes you can get faulty equipment out of the box. Try checking for unnecessary hot part after you turn your computer on, might help you find out what the problem is.

To tell you the truth I would take it to the person who sold it to you and ask for their help. If that person still cant get anything to work then tell that person to refund your money and goto:
http://www.newegg.com

It may cost a little bit more then a used mobo/cpu, but you might not be able to get the mobo to work period. I have had trouble with the computers I have built and sometimes you can fix them and sometimes you cant. Take the easy route and buy NEW. Only my opinion though.

Good luck

In "unplug everything," did you try removing the DVD and HD? I know you will eventually need the other in order to boot, but I have a feeling its one of the two. I've seen a USB external HD cause a machine to fail POST repeatedly.

If it doesn't fail without either, try adding one, and then the other. If the DVD drive works, try a live CD. If you've got another HD, try that one. You should start with MB+CPU+RAM, NOTHING ELSE.. no pci, no agp, no ports, no mouse, no HD, no DVD and work your way up one peripheral at a time.

thanks for the replies...I've already gone the route that adm_strat suggested, having ordered a new mb last night. I've come to the conclusion that either the MB or the BIOS chip is bad and Im tired of messing with it...

Sounds like the Mobo. It might even be a case fault. Have you tried testing it on a bench, rather than in the case? I have a case and Mobo a few years back that worked fine with other components. If I put that Mobo in that case, though, the damned thing simply would not POST.