I use Gparted too.
-First go to that site and download GParted
-Then burn that program as a .ISO file so that your system can read it at startup
-Put the CD into the CD drive and restart the computer (it should ask you too press any key to boot from CD, if it doesn't and just starts going back into XP you'll have to go into your BIOS and select your CD drive as the first boot option)
-Select the option you (i believe it is the first one) want then resize the one drive to however many smaller drives you want
-Vista requires 20 gig empty space to install, XP requires i think like 4 gig, and Linux Ubuntu can run on like 5 gig
-Pop in your new OS CD and install on the empty partitions