Non-Destructive Partitioning with GParted
Blogcritics.org goes over repartition a hard drive with the GParted LiveCD.
“Okay, little Percival, let me tell you what partitioning was like in the old days. If you already had information on your hard drive, but wanted to re-partition it, all your data would be erased. There were programs available that would partition your drive without erasing all your stuff, but they cost money.”