Wubi

Wubi is a software that you can download and it can give you a dual-boot operating system computer.  That means when you start the computer up it will have a options screen that will say "choose your operating system."  Then 2 options will come up.  Ubuntu and windows.  This will only work with windows unless you find a mac version or something.  With wubi you can get Ubunntu, Edbuntu, Mythbuntu and many others.  Ubuntu is the most advanced version and I would recommend that you get it if you are going to use this.  If you don't want the dual-boot anymore, you can just go to "programs and files" then delete wubi.exe (or it could say Ubuntu or one of the others).