I'm 5 boxing WoW atm.
It means I have 5 bought accounts of World of Warcraft, each of which allows a one concurrent character per copy of the game. There is software which allows to manage multiple characters at once, but I've hit some performance issues.
I've got athlon 2.2ghz with radeon 9800 atm, and it can smoothly run 2 instances of the game at nice settings, but at 3 instances, not all of them run smooth.
Another machine is a lowly 1.7ghz running at 1.1ghz (only lvl it's stable), and it can only handle 1 game instance smoothly, and 2 when forced - but at bad response speed.
So I need a cheap machine capable of running 3 game instances smoothly, and the cheapest one I've found (new) is about 470e. Vista with 2core processor and 2g ram, some video card I don't remember.
Another chance is to buy a used 2.7ghz machine with 120e and run 2 game instances with it, 1 with 1.1g and 2 with my 2.2. Oh the power consumption
My main unknow issue is how to handle multi-graphics processes. I know all about CPU multitasking. But 3 graphics-intensive processes take on GPU resources as well, and GPU's aren't designed to be part of a multitasking system.