You can't install all the operating systems out there. You don't have the time, the energy, the money or the motivation. I mean, your XP seems to work just fine. Why would you install a Linux distribution? And what Linux distribution?
There is a site called OSVids.com that has screencasts from many operating systems, including Ubuntu, Fedora, SUSE, Debian, OpenBSD and Vista. For some of them, you can see the setup, for others the desktop and some basic applications. It's really nice to sit down and compare all these operating systems. Maybe this way you'll decide what Linux distribution you'll install.
Missing from this party are the old versions of Windows (but you probably know them), Mac and Google Operating System (who is not yet ready to be launched).
Will Linux rule the world? (read the comments)
Partition your hard drive without Partition Magic