I just bought a used CNC router, cw really old PC with parallel port. It died on day 2 of my playing with it. I went and bought an older HP off Kijiji for 100 bucks, running XP pro. I loaded all the software non it and it was up and running with no problems. I have not yet switched to Mach3, because then I would need to upgrade the controller to run it. $300 ready to go. I am still a newbie trying to figure things out. I am finding even the demo version of Mach 3 is a large help to me. For those who want all the bells and whistles, do like an acquaintance of mine and spend $25000. Hardly a hobbyists set up.
Given that I make an awful mess in a very short time using it, I fail to understand how anyone would be using the same pc machine to do other work in their shop. but thats just me.