If you are looking to try a new OS, but are a bit hesitant to wipe what you have and start fresh a dual boot is a great way to transition. This way you can try the new OS while still having your old OS operational to make the transition easier.

With that said, if you are unsure how to actually do this, take a look at this dual booting guide posted on APC. It shows you how to how to create a dual boot with any combination of Linux, XP and Vista. No matter what OS you are starting with or what OS you are transitioning to, this guide an help.