If your interested in something to get you feet wet, try slax www.slax.org
It can be put on a USB Flash drive and boot a computer.
I use Debian, Ubuntu and Fedora-11, but keep slax in the bag as a handy tool.
As they have all said, the best linux is the one that suits you best.
Get an external HDD so you can try many and not mess up the XP, any more than it is already.