alright, the biggest problem for Linux beginners is usually the install procedure, especially partitioning and bootloader issues when trying to setup Linux in a dual OS environment together with XP. I found a nice way which makes this much easier: you can start the install while on XP and the rest is (almost) running automatically!
there are 2 Linux distributions which support this: Debian and Ubuntu.
Debian is my favorite, but it seems the Ubuntu install is even easier because you can use the existing partitions and don't have to create a new one like with Debian.
k, first the link to the Debian installer:
http://goodbye-microsoft.com/
when you have downloaded and started the Debian installer you'll be asked if you want a textbased or graphical install procedure, then the computer reboots and you'll find Debian as 2nd OS in your boot menu. when you pick it a partition for Debian will be created and all needed files will be installed via the internet (so it is highly recommended to have a fast connection, same for the Ubuntu install).
here the link to the Ubuntu installer:
http://cutlersoftware.com/ubuntusetup/
installing Ubuntu don't even need the creation of a new partition, it uses the existing one! but well, they say it's still experimental.......on the other side it can't be more experimental than Vista I guess...
on both installs the existing XP system will NOT be removed, after install you'll have a dual OS system.
enjoy!