bluejay

But before that I can try a spare motherboard I have. It's got a problem though, it makes a really weird high pitched whining noise when I power it up. It's not the power supply, I tried swapping it around with my good machine and confirmed that it's the motherboard that's bad. I think it's a little capacitor that blew, so I'll have to replace that, but if I do I'll see if that one works.

I don't know, shipping the whole thing would be much too expensive. Shipping just a motherboard and a controller card and a power supply and a keyboard would be cheaper, and you could test it with your own CGA card and floppy drive.

If you think shipping it in bits is a bit overdoing it keep in mind that the whole computer weighs about 10kg, and it's about as big as a sewing machine.

Should I ever work on your rig I would want the whole thing. It's the best way to repair things like that. But, sure, try the motherboard.

And check for hot capacitors. A thermal camera helps, and they're becoming more standard in any technician's toolbox nowadays. Just 10 years ago they were still expensive.

I had a GF who had a Compaq Presario in 2001 for a few days,  Unfortunately the thing was such a junker, we had to take it back and get something that worked.