First, I just wanted to say that I've just upgraded to Win10 on a new mini PC and UC100s on both my machines, with very few issues, so there should be light at the end of your tunnel!

My original setup had an XP machine with parallel port drive through a port changeover switch to lathe and mill. My first step was to just install the UC100 plugin, fire up the lathe Mach3 profile, select the UC100 on the dialogue box that came up, and I was away. The only config thing I changed was on the UC100 plugin control where I changed the pulsing rate from the default 100 kHz to 25 kHz (which I had selected for the parallel port). So all the port&pin configs that I had set up for the PP just worked with the UC100.

Then I tried the same route on the mill profile and again it just worked.

I then had a little detour where I explored the increased pulsing speed of the UC100 on the lathe to try to get smoother stepper motion. I found that I couldn't do 100 kHz as the stepper drives didn't have an appropriate microstep setting; and 50 kHz was hit and miss. I eventually decided that the drives were limiting the set rate and reverted to 25kHz and it works fine.

This could be something that is affecting you - if your Z stepper driver is a bit marginal try (a) reducing the step rate in the UC100 control and (b) increasing the "pulse width" setting in the motor tuning config box to its max (5us).

On the mill, which has more up-to-date stepper drivers, I have been able to increase the pulse rate to 100kHz and up the microstepping ratio, giving smoother motion.

End of part 1!