Oh what's that little PCB in the slot next to the CPU? I seem to recall it was cache memory but not sure if it came with the mobo or was something I bought separately?

That's a COAST (Cache On A STick) module. Depending on configuration it can add cache to a system without cache, add more cache to a system with some, or add an extra TagRAM to enable more memory to be cached. Given this is an i430HX system, it could be any or all of the above.

Super socket 7 motherboards are a special case that makes them expensive on ebay. That is why this system seems less expensive.

Those are some interesting 5.25" devices... the top one looks like speakers? And the 4-disc changer is rather uncommon, while the CD writer has to be a *really* early one seeing that it takes CD Caddies.

Anyhow, for keyboard, you can purchase a 5-pin DIN-to-PS/2 adapter. Serial-to-PS/2 adapters for mice exist but require that the PS/2 mouse in question supports operation over serial.

Yes, that top 'drive' is a pair of absolutely awful speakers. I had the same for a very, very brief time 😉

Yes defintely top one is speakers. Another reason I am sure someone robbed the soundcard out of this PC - and the voodoo 2. HAving said that I sold this PC in the 90s and just got it back again for free so really can't complain 🤣

Not tried it with a CD but the 4 disc CD changer at least opens the flap if I press each of the four buttons, You feed discs in to the opening, it does not have a tray.. So mechanically it is working but not able to test it functionally yet, I don't remember if it appears as 4 individual drive letters: but suspect it does. Will have to look to see exactly what the CD writer is but yep it is an early one as had a computer shop at the time 1993-2002 and was always grabbing examples of the latest tech for myself.