How to start applications more than once (ie. defeat a mutex)?

[Craisins]

I remember there used to be a game I'd play online but you could only launch one instance of the game, but there was a program where you would type in the location of the .exe of the game and it would launch it as many times as desired, taking up more and more memory with however many you launched.

What does this consist of, if I want to make my own multi-launcher?

Edit: I still have the application, and it works for anything, not just the game exe. I just opened 5 Windows Live Messenger applications and logged into 5 different accounts at once. I suspect it opens things in their own memory block, but I have no knowledge of memory editting, so don't mind me.