I honestly don't have an answer for this and I've looked into it on multiple occasions. It seems if you want to run one PC as several computers it just can't be done. Each one would essentially have to be its' own separate terminal. You could run it as VRM but splitting it into multiple displays with keyboards and mice would be a different challenge altogether.
I suspect this could be done by virtual machines just to get a few different computers running. The next challenge will be possibly the hardest, the Input for all of them. My guess is if you are going to want to do a LAN party between these computers (and only play games) a Controller MIGHT work but it would never be perfect. If theres software out there, then this would be perfect. The next challenge would be getting all those virtual machines into full screen.