I'd check all fans for seized bearings (can be intermittent) and dust clogging the heat sinks. You may have to open up the power supply box to clean it out. My kid's computer got a blue screen and trashed the hard drive seriously. I found the CPU heatsink was totally blocked with dust. It blue-screened a couple times after being on a half hour or so. After vacuuming all the dust out, I had to reload the OS. It has worked fine since then.
I didn't read the motherboard BIOS material, but often, info that's included in the manuals often doesn't apply to all versions of any models of motherboards produced.
Then there's the aspect of flashing the BIOS to obtain updated features.. and whether it's been done, or if it should be done.
You might find some related information in the recent post: Subject: OT-Odd (to me) computer failure Date: Sat, 14 Jul 2007
I've never heard of any consumer grade PC that outputs motherboard diagnostic parameters. There are add-on cards that will monitor all kinds of parameters from the ISA or PCI buss, and sound alarms or make other corrective measures to safeguard the system. These cards are essentially computers themselves, built for a specific purpose, and I believe that they do output reports, or at least logged diagnostic parameters into their own memory, which could be printed out when desired.
There are also some cheap diagnostic cards that come with manuals containing code lists, to relate to a code displayed on an led display located on the card. These are installed in a slot prior to the power being applied, and their primary use is to check POST conditions from the buss.
About the only measures most folks can take to keep a system in good operating condition, are to insure that the board is kept clean, and that the CPU is protected from overheating. These also apply to the power supply.
It was suggested earlier that the chances of building a reliable system would be limited, when using "used - tested good" parts.
Many new systems have hardware monitoring built in, but I have not seen one with data logging.Could likely be done with a bit of patience and a lot of knowlege in programming.
As for building a "reliable" machine from "used - tested good" parts, you actually have a BETTER chance than with new parts. With "experienced" parts you know that they at least worked ONCE - with the new crap being sold today, there is a significant chance it both never has, and never will, function(ed) properly.
I've built up a lot of systems with "Experienced" parts.
Yes -- some UPS models check the battery every so often by switching over to run from the batteries for a few seconds and monitoring the voltage during that time.
If the batteries are getting tired, you will loose the power and reboot.
If the batteries are fine, but you are at the top edge of the capability of the UPS (or beyond), you will also experience this same problem. it is better to not exceed 75% of the capacity of the UPS, though I am currently guilty of running at 86% while I am migrating everything from an old server to a much newer (and faster) one.
If you have a laser printer hung on the UPS along with the computer and a large CRT monitor, you could have excess load at least when the monitor is on and the laser printer cycles on the fuser coil, so that combination could force a reboot.
If I'm not mistaked, the original "used - tested good" evaluation came from an ebay seller, so it all depends upon what his interpretation of good is.
Yours is a valid point, and I decided not to comment about the quality of newer products in my last post. When the original idea to buy a used motherboard, not absolutely Known to have ever operated properly, came up a number of weeks ago, I thought it was a poor choice for a machine controller.
I realize the value of older stuff, and I like using it myself whenever I think it's practical. I built my first (286 8MHz) PC in 1992, and hadn't bought a store computer until about a month ago.
The OP's present options are probably limited to changing out the CPU, ram, video, PSU and then replace the motherboard. By then, there may be 2 CPUs of unknown working order, and various other duplicate parts left over, that might not be of any use on down the road. Otherwise, it could be a wrong clock setting (overclock overheat), the incorrect ram, or any one of tens of thousands of PN junctions somewhere in the CPU or on the motherboard.
The OP would've had a much better chance of success if the doofus seller had just left everything on the motherboard, but instead, he had stripped off the removable components.