Drivers operating in erratic way

[dazp1976]

That's the forth person I've seen that's been having problems and been using a UC100.
That thing really seems like fitting a band aid that was quickly bought out when PC's started removing the parallel port.
Connector converters have never been very reliable.

Dump the junk and get a UC300 or 400ETH, a couple of cables and bob's. Save yourself hassle.

This is the way I'd go in the future when I eventually need more pins. UCCNC / Servo spindle / Toolchange etc.
As it is my £40 Dell refurb (with actual p,port), WinXP, £7 bob & Mach3 have been faultless for over 3 years on 3 axis.