I helped a customer today use who wanted to make some changes to the partitions on his external drive using Drive Genius 3.  He had 2 partitions on this drive but decided he wanted to delete one of the partitions and then add the remaining space to the main partition.  He called support for assistance because wanted to make sure he was doing it correctly without ruining the main partition on this drive. I guided him to the Repartition tool in Drive Genius 3 and had him delete the unwanted partition. Then he was able to select his main partition on the drive and resize it to account for the remaining free space. He was very happy that he was able to get rid of the extra partition and keep the remaining storage space without having to reformat the drive.