LOL, virtual machine is an operating system that runs inside your operating system, you can buy Microsoft Virtual PC(or download it from the right places), or use VMware, i use VMware as it works better. You load the program and it will allocate whatever amount of diskspace you want to use and whatever amount of RAM you want to use to the virtual machine you are going to "build" you then have to install another copy of windows just like it was a new machine, but the new machine runs in a window of the real machine, you can easily network the two machines and everything runs JUST LIKE you had two different machines setting side by side.....Lots of big companies use VMware on very powerful servers...meaning they can take one very powerful server, load 5 different virtual machines on it and make 5 servers out of it. You need at least 1GB of RAM i would say, although you could probably make 512mb work. And say you get a virus or a file corrupts your "virtual" machine, who cares, its not part of your real operating system anyways