agh:
VIRTUAL COMPUTING: When one OS is running inside of of another, in this case windows XP is running inside of windows 7. see VMWare (VM ware works on BOTH Windows and OSX)
MULTI BOOTING: When more then one OS is present oft he computer. one needs to shut down in order for the other to start. called "bootcamp" on OSX for some handicapped reason. Linux uses GRUB (usually), windows has no name for it.
I swear when I hear people talking about bootcamp as if its a virtual box I want to pry out their eyes with a screw driver. Gen. Nick, your acting like a douche on this thread. Mac users can emulate Linux or windows 7/xp if they have the right equipment. However windows users might not be able to, because macs are handicapped about what hardware they support so they don't work on computers that have parts that haven't been graced by Steve jobs.
tl;dr: shut up Gen Nick, you have no clue what your talking about, but neither do most of the people in this thread.