If you have ever partitioned your hard disk, Partition Magic would probably be the application you used for it. It’s probably the de facto software to use for doing anything with partitions with a very low chance of any loss of data (I personally have never got any issues on data loss/corruption). Unfortunately, Partition Magic isn’t free.
I recently tried out GParted (stands for Gnome Partition Editor) to repartition the hard disk on my Ubuntu server box. As opposed the Partition Magic which runs only on Windows, GParted can be used regardless of the operating system installed. It boots up via a CD or USB (which you can choose from the site) and is able to support the file systems currently in use by Windows and also Linux.
Its interface is very similar to Partition Magic, so it shouldn’t be too difficult if you have prior experience with the former. I managed to delete a redundant FAT32 partition I had and resized my /home ext3 partition without much drama. After restarting, everything was in a perfect order, so I don’t really have much to complain about.
Try it out if you’re looking for a free, open source alternative to Partition Magic.