There was no shortage of fucking around to get to this point, but I've now transferred the contents of both hard drives to a CF card and we have had a distinct reduction in whirring and the occasional worrying CLONK noise.
Also I can now get data on and off the PC easily which means I've actually achieved what I wanted from this. I now have a way to get data off a 5.25" floppy disk and onto a modern computer.
I have built literally hundreds of PCs from this era, and this one is everything I could have wanted as an example. It's old enough that there's nothing extra built-in to the board - no HDD controllers, serial ports, nothing - so less things to go wrong and it's easily tweaked by using expansion cards.
Also, it's new enough that the BIOS isn't completely confounded by hard drives that may be a little larger than was common and handles something like a CF adaptor without issues.
Highly likely that you or I built this thing, @FunkyBob - that's one of the old shop's inventory stickers on the modem, isn't it?
Heh, I had noticed the clock didn't seem to be working properly in the computer (and might have Y2K issues). I was thinking it was probably a battery thing, then found a note in the autoexec.bat file left by the previous owner saying that the clock had never worked.
Thanks for the note, saved me a lot of time!
@mike Now you've got me looking up PATA SSDs to put into my PowerBook G3, and ATX power supply replacements for my Mirrored Drive Doors PowerMac G4 whose PSU is on the way out.
@virtualwolf I think Compact Flash card adaptors are the way to go on stuff of that era. They're plentiful, cheap and being able to pop them in a USB card reader to transfer files back and forth is a huge timesaver. Much easier than getting old stuff networked sometimes.
Consider this a friendly, local pub. Make yourself at home, bring your friends, have a good time! Meet new people, have a laugh, enjoy the ambience, and the Oxford commas.