It's quite easy to set up dual booting. In my experience, the easiest distros to do this with are OpenSUSE and Mandriva. I recommend either of those. Another good thing these distros have is a centralised "control centre", a bit like in windows. In SUSE it's called YAST, and in Mandriva it's "Mandiva Control Centre".
Then once you have it installed, you generally want to install multimedia stuff like flash, realplayer, DVD watching etc.. , and want to set the computer to connect to "software repositories" to get all the latest and greatest soft. For SUSE, this will be a great pointer: