I have a kind of wierd issue. My pc will boot up fine in the mornings. If i ever have to do some hardware swaps or hard drive upgrades or anything that requires a restart, my pc wont post, I can't even get a monitor turn-on. Some times at random I will get a checksum error, this is usually what starts it. I replaced the CMOS battery when I first started getting that error. So usually when I get that error, I reset time, date, and all the bios settings....save and close which does a restart and it never does restart, just the dreaded no beep, no monitor, no nu-ting (nothing) . I believe there is a bios update which adds some wake up on lan, and some other option to the bios menu, nothing major. I may acually have that update already, but I don't want to flash it unless I have to. What other things could be causing this issue? I want to think it is a mobo issue, since I've tried it with no ram, expansion cards, or ide cables on the board and it still does it. Could it possibly be overheating that often? I've put a desk fan pointed directly at it and still no help. What am I overlooking, or what else might be the issue? Any Help please?

If we came up against this with a customer, we'd have to treat it as a motherboard issue of some sort.

If it was overheating that badly I'd expect there to be problems turning it back on immediately (and I mean power - not just no POST).

Does your BIOS have a temperature monitor in it?

Any USB damage? What if you disconnect the front board, for example?

What about running RAM and HDD diagnostic tests just to eliminate those?

Does it do it when you just power from mains (i.e. eliminate peripherals from the equation)

You've actually done far more than we'd expect our customers to do and it all points to a mobo issue.

You've just described all of the sympthoms of the dying bios battery. It might have aswell corrupted the bios, so flashing (or re-flashing the same version) is advisable.

thanks fellas. I'll check the hard drive and ram , and flash the bios tomorrow.
If that doesn't uncover something, it's rma time