Okay, VMWare is a program for Windows that will allow you to install and run any other OS (with the exception of Mac, as far as I can tell) from inside Windows, by creating a "virtual machine" on your hard drive.
You start the program, then create your "virtual PC", then install the operating system you want onto that "virtual PC." Right now, I have SuSE 10.1 Linux installed. No formatting needed, the OS just sits in a block of hard drive space set aside for the VMWare program, and when I decide I'm done playing around with Linux, I just delete the virtual PC, no reformatting needed.