Re-Partitioning using Partition Magic 8

I have a Sony notebook running Windows XP Professional with a network connection. My 15 gig hard drive is configured 5.63 in C:, with 8+ gigs on the D: partition. I bought PartitionMagic 8 and will attempt to use it to increase the C: partition. I get conflicting reports regarding the advisability of doing this and have been told to back up the disk, reformat, re-load the Operating System, programs and data. I have backed up, but would like to re-partition without going through the hassle of re-formating. Any advice? Al Aramburu, basque216@sbcglobal.net