After my last post I managed to find some reasonable deals on a graphics card, a Nvidia Riva TNT2 Pro 32MB and a SB Live Value! so I ordered those, and they showed up very soon after.
I hadn't yet received the motherboard and CPU, so I decided to try the graphics card in my Athlon XP PC which hasn't worked in years, and I had a strong suspicion the problem was graphics related but as I lacked a replacement AGP/PCI card I never got to the bottom of it.
While it didn't immediately solve the problem, it did change it as I now started getting POST error beeps! It would give me one long beep and then power off, reminding me of the classic Red Dwarf episode "White Hole" (wikipedia) where Holly overclocked her I.Q. giving her minutes to live and turning herself off to preseve what was left but I'm the naive Rimmer trying to force it back on! Online discussions suggested it might be a safety protection for the CPU fan, which was working but I thought I'd try another in any case and the damn thing booted!
The fan I removed had been there for many years but I when the on-board battery died it reset the CMOS and the default option was "Halt on all errors", which includes a slow CPU fan. Because the fan was of the low-noise variety it spins at a leisurely 1,500rpm and the motherboard didn't like that, it wants to feel the wind through its heatsink, so the replacement fan spins at 2,500rpm and sounds like a vacuum cleaner while doing so, but the motherboard is much happier with this.
After solving this problem, I got another, more familiar error beep, this time it was memory related. I identified one of the 3 SDRAM DIMMS as the culprit and pulled it, now the system was happy to boot with 512MB RAM (spoiler alert: it wasn't), and boot it did, many times I tested it in astonishment as I could not believe I'd finally fixed the board I'd almost given up for dead but I'm too stubborn to give up on old tech, which is necessary when you have 3 independent faults to work through.
A few days later the Pentium II motherboard arrived and I eagerly went to boot that up too, but sadly it was dead on arrival. It would not even start the PSU up let alone fail POST. I spent several days trying to diagnose the fault with it but eventually I gave up and asked for a return which the seller graciously accepted.
Now that I have a working Athlon motherboard though I decided instead of targeting the 1st generation of this build, I would instead target the 2nd generation since this is the motherboard and CPU from the system I built around 2001 to upgrade the Pentium II! It is a turn of the century system rather than late 90's but it still pre-dates Windows XP, I ran Windows 2000 on this system at the time, and SUSE Linux, but I think in this initial stage I'm going to still roll it back to Windows 98 and give that a good shake first.