The CPU is not seated properly -- unlikely. I aligned it right, checked and triple-checked, and set everything exactly as it should be. It fits just as it should, too.
CPU is overheating -- I don't see how this could happen with a cold CPU with a functional sink and fan within three seconds of powering on.
The CPU is defective -- this seems like the most logical, but both CPUs dead when they worked only minutes ago? Did I break them? Or,
The motherboard is defective -- I haven't the foggiest if this is more likely than a CPU issue or how to better test it since I have no other Socket 462 motherboards on hand.
I'm beginning to think that I might have damaged the CPUs somehow when removing and installing them. The pins all look fine. I am fairly cautious about static, but I don't own a wristband -- could that have caused it?
One more clue: I found another Athlon CPU, not sure exactly which, but when I install it, the board does NOT sound flash or beep. However, it does not enter BIOS or do much of anything -- after a few seconds, I hear a lot of clicking from the CPU. Otherwise, nothing. I hate to overcomplicate the issue, but I don't want to leave out anything important.
OEM Windows XP
BIOS: Phoenix Tech 12/02/2004 (the update I mentioned: http://support.gateway.com/us/en/emac/product/default.aspx?tab=1&modelId=1439)
Old CPU: AMD Sempron 3000+
New CPU: AMD Athlon 3200+
Edited by Arc042, 28 July 2011 - 09:24 PM.