Not sure if that motherboard has a speaker on it to give BIOS beep codes? You could try fitting one (photos of that model MB show an obvious spot marked buzzer) and seeing if it tells you anything. Is there on board video (I can see an HDMI port)? If you do get video, at what point does it freeze (during memory test, disk detection, loading the OS, ...)? Thermals could be an issue. Some media servers hardly stress the CPU or RAM, so it could have spent 7 years barely being warm, except during booting. Also, strip everything back as much as possible: motherboard, PSU, CPU, one stick of ram, one video adapter, all bios settings to defaults, bootable usb stick with memtest (I'm assuming it boots from usb).

And try changing the capacitors. Or at least have a close look at the aluminium electrolytics (and on the back of the PCB under them). I just got an old Soltek QBic with an SL-B9D-FGR and Athlon64 3000+ Venice running again. That's a socket 939 from around 2005, so only a little earlier than yours. Around 4 out of the 6 capacitors near the CPU had bulged and some had leaked. Only one of them tested ok. My older '99 ABit KA7 was even worse, with one of the power FETs managing to singe the underside of the PCB. Plenty of examples on https://www.badcaps.net/index.php of failed capacitors on stuff a bit newer than 50 years old. Efficient troubleshooting (which I'm not always good at) generally means starting with the common faults first. Like capacitors.

JonnyGators wrote on 2021-03-29, 20:13:

Does anyone around here know how to actually troubleshoot motherboard problems?

An ASUS A8N32-SLI. Was my 2nd build, bought it in March of '07, along with a Athlon 64 X2 3800+. Was my main machine until 2013. Then it was used as a secondary machine - had XP on it for a period of time to run some apps that didn't like 7. At some point it started giving me some random problems not wanting to turn on all the time, and just kicked around not doing much. Never really knew where the problems were, never really spent much time troubleshooting it. So about a year ago I decided to play around and see what it could do, and if problems came up I'd deal. And I managed to successfully build it into a open media vault media server. Had it running 24/7 for quite some time. It didn't like booting up properly, even with a new battery it usually loses BIOS settings when unplugged, and often I have to go through the setup a few times to get it to boot to the right HD - but once it booted, ran stable, never a problem hosting the terrabytes of data on the RAID 5 that was in there.

haven't run RAM tests on it, but the RAM has been sitting in there for years running things

Many members here do know how to troubleshoot a board, some even at the logic level. For the basics start with these:
First: " It didn't like booting up properly, even with a new battery it usually loses BIOS settings when unplugged" = bad sign of something corroded or failing.
A good board will not loose cmos over a few months with a new battery.
Second:
As snufkin said: speaker on it to give BIOS beep codes? And do not discount bad VRM caps.
Do you have a POST Diagnostic card ? Boot the system with it and record what ever the LEDs tell you.
Why have you not run a memtest ?
After a few years the heatsink goop will dry out, have you pulled the heatsink and cleaned+re-gooped it ?
Corrosion can develop in the memory, PCIe, pci and isa slots or on the cards themselves, have you pulled them and cleaned the edge contacts with ISO alcohol ?
Have you tried booting without any HD connected ? when some fail they can make a system not boot. Are you talking all 2007 era parts ?
Thats my quick take 😀

Excellent stuff I will have to hold onto and keep in mind, as I work with more mobos.

After some more fiddling around - I discovered the random freezing issues stop when I disable all onboard devices that I can. I disabled several of these devices when running it as a media server, so that explains why the problems never came up in the time I was using it for that.

I think I have a damaged battery holder - I've tried to adjust things to make contacts touch the battery - but that hasn't seem to have worked. Probably replacing the battery holder would do the trick to get the BIOS to hold it's settings.

I was hoping to install Vista on it (an OS I never used - but the OS of the time of this mobo, so may as well tinker with it) - but it doesn't like to install it from a usb key, and I haven't had much luck getting a clean DVD burn of my image. I have an XP-64 bit disc kicking around, throwing that on for now - and then will try turning on onboard devices one at a time to zero in on the problematic one.

I really don't know what to do with this mobo anymore - but having had it in use for much of the time from 2007 up until now, it's kinda sad to power it down and store it away. I want to find something useful to do with it - but nothing really comes to mind. I'll probably just tinker around until I get board, and then dig up the original box and store it away - with a note of what needs to be disabled in the BIOS to make it work right. At the moment, it kinda falls into an era of not old enough to be interesting, not new enough to be useful for much anymore. Although - it is around the time of the end of ide connections being standard on motherboards, and it has 3 PCI slots, which I remember having to shop around at the time to find something with more than 2.

JonnyGators wrote on 2021-03-30, 04:45:

After some more fiddling around - I discovered the random freezing issues stop when I disable all onboard devices that I can. I disabled several of these devices when running it as a media server, so that explains why the problems never came up in the time I was using it for that.

That sounds like it may be a chipset or some other onboard function. Have you tried enabling devices one at a time until you find which is faulty? On my daily driver (FM1 motherboard with A8-3870K APU) the onboard network failed, and I had to disable that in the BIOS and buy a cheap network card (I plan to switch to another system built around a Maximus VIII Hero and i7-6800K soon)