There are many different ways. You could torrent XP, which would take a really long time to download, and be very buggy just because it isn't a legit copy. You could put this torrented XP onto your computer's hard drive as a second OS, still buggy of course, or you could use a virtual system, like VirtualBox and then install the torrented XP in VirtualBox and not mess your computer up at all. If you go with VirtualBox, make sure you have at least 6GB of Ram in your computer, or it will be extremely slow. Also, make sure your computer can handle running VirtualBox with an OS in it.