I haven't used my cnc router in years.  It has parallel port breakout board and I have a license to Mach 3.  I would like to start using the router again, but all of my computers now are 64bit Window 8 or 10 and no parallel port.
I would like to buy a USB or Ethernet motion control board that will work with Win8/10 and Mach 3 but would like to be able to use Mach 4 sometime in the future.
Is there a motion control board that will work with both Mach 3 and Mach 4 and does it work with Win8 and 10?

Thanks

ESS or pokeys 57CNC or 57U or 57E

The Warp9, Ethernet Smooth Stepper will operate with both Mach3 and Mach4 http://warp9td.com/

Tweakie.

same with pokeys

CSMIO, Vital Systems are another 2 manufacturers thats products  will work with Mach3 and have they plugins for Mach4.
 Don't think there is such a thing as a controller that works with Mach4, at this time,  which can do all Mach3 can. That however is most likely because Mach4 can not do what Mach3 can at this stage. What the future holds I don't know but likely if you choose any controller that presently works with Mach3 and is NOT Chinese, then it will likely support Mach4 when Mach4 is reliable and ready for main stream. One exception to that however is, I THINK, the Kflop, as far as I am aware there are no plans for a Mach4 plugin for it.

Hood

Other exceptions may be the UC100 and UC300.
Since CNC Drive has written their own software, they may not be supporting Mach4 with their hardware.