You will want to move the data to the partition that you want to delete before deleting the partition. If the capacity in the partition is not enough then you must backup the data onto a separate hard drive. At the worst you want to backup to DVDs, but since you can only backup 4.7GB on a single layer DVD / 8.5GB on a dual layer DVD, you are going need to burn at least 1 discand it's very likely you will need to burn multiple discs. That will take a lot of time to burn then verify the data, then copy the data back to the hard drive.
Needless to say, backing up data to a different hard drive is a much better solution.