Hi,
Gerry is right, Mach4 and an external controller such as he has mentioned are sort of 'native' to each other.
Mach4 does have a parallel port option called Darwin. There is a $25 fee to use it. It also has the same restrictions that applied to the
parallel port of Mach3, namely Windows 7 32 bit or earlier. Given that your problem comes from Windows 7 updates then Darwin
is probably no closer to a reliable solution.
I use an Ethernet SmoothStepper, it costs an extra $60 odd than a UC100 or PMDX-411 but it has three output ports for much increased
numbers of inputs and outputs. If all you require is to get your Sherline working with the existing Xylotex driver then the extra ports
(and expense) are of no importance to you, unless you wanted to expand your Sherline and therefore required more IO.
Craig