Partitioning the System drive

I originally had a dual boot system on my PPC Mac Mini. I'd now like to have a single boot system with only OSX. I deleted the other system, and it's partitions, but now I have free space at the end of the drive. How can i get that free space back on my first partition?

I had originally planned to back my entire HD onto an external USB drive, repartition, and restore. I booted with my Install DVD, went to Disk Utility, and found that I couldn't mount the USB disk, even though it was detected. Would I be able to mount the disk if it were not in Fat32 format? Is there an easier way to do this?