Merge or Combine Two Partitions in Mac OSX
1. boot from DVD (10.5 system disk / Leopard)
2. open Disk Utility
3. Select the hard drive from left hand column (NOT partition but drive, eg something like WDBEVE and not s03 etc).
4. Click on Partition tab in main window
5. Select "Current"
6. Select partition you wish to delete
7. Click on minus (-) sign on bottom left
8. Confirm Delete
9. Drag original partition to include full disk
10. Confirm resize
That's it! Reboot and you're done.