Hi,
if you are using Mach3 and an XP PC I guess you are using a parallel port? If so and you wish to stay with the parallel port there are limited choices.
Machs parallel port WILL ONLY RUN on 32bit Windows 7 or earlier, and that will limit your choices to old or very old PCs. If you can find an old PC but does not have
a parallel port you can fit a parallel port card. Note however only some of the parallel port cards work properly with Mach, you need one of the original MOSTEK ICs,
there is a specialist seller if you need one.
If you want to use a 64bit PC or say Windows 10, then you will need an external motion controller. I use an Ethernet SmoothStepper ($190),
but there are others cheaper, like a UC100. Note that if you buy a UC100 don't buy a knockoff Chinese made copy from Ebay or Amazon, get the real deal
or don't bother. I would not recommend any of the cheap Chinese motion boards, they don't work well, if at all, and often only with pirate copies of Mach3.
A PC to run Mach does not have to be powerful. I run my mill, and have done for seven plus years, on a 32bit dual core Atom PC without a graphics card,
well less than is recommended for Mach, but aside from being slow to load big toolpaths files it works fine. One of the kids cast off school PCs or an old
gaming PC would be fine.
Craig