Mouse Driver Not Loading w/ Errors

I have a couple of older NT workstations (4.0/SP6) that the serial mice have stopped responding on. I'm under pressure to get at least one of these working and am out of options. Here's what I've tried so far:

*Unplugging and replugging the mouse.

*Changing the mouse properties to Serial mouse (even though they were set as such already)

*Making a registry change to force it to use the mouse on a serial port

*Bought new mice and loaded third party drivers.

*Tried an ATX Form Card which supplies PS/2 funtionality to these older motherboards. Motherboard doesn't have the 18-pin spot required.

*Installing (re-installing) the latest service pack for NT.

*I think that about covers it.

*Checked the boot.ini for the /noserialmice switch that may be preventing mouse detection

Most people say "upgrade your computer", but that's not an option. This PC needs mouse funtionality, but I really don't know what the problem is anymore. I get a "service failed to start" message when the Desktop loads, which upon closer inspection turns out to be the mouclass driver not loading so I know it's somehow related. The problem there is that I get this same error on other PC's and the mouse continues to work fine day after day.

So any thoughts on this problem? Anyone? Please? Help?!?!

Thanks in advance if you can,

Jeremiah