I am looking at a Pentium 166 which has USB support in the BIOS but no plate connected to the motherboard therefore it has a PCI / USB expansion card fitted.
USB worked fine with just a modem, but as soon as a USB printer is added you cannot use the modem - port busy.
Both hardware will work OK on their own.
I believe I have traced the problem to an older USB modem that I cannot remove from the registry. I have removed the card and USB in Control Panel/System/Hardware Settings but I cannot remove in the registry:
HKEY_LOCAL_MACHINE\SYSTEM|CurrentControlSet\Enum\USB or anything below (which includes the old modem references).
I receive the the message: Cannot delete USB. Error while deleting key. Sorry, no points for advising me to re-install 2000.