I recently moved from a G-5 desktop to a Mac Pro using Mac OS X's default data migration option which is available the first time you turn on a new Macintosh. The only problem was I forgot about the other disk partition I have which is running Leopard (Mac OS X 10.5) until all my data was migrated. Now what do I do?
Repartition on the Fly
The answer was simple. I used Apple's Boot Camp beta partition option to dynamically create a new disk partition. Of course, Boot Camp thought it was going to install Windows on the new partition. Instead, I just installed Leopard.