I had bad luck when I attempted the ONLY time to use partition magic. It screwed up my partitions but thankfully, I was able to get the data back. (please excuse me for not providing details as this happened a year or so ago and I can't remember WHAT I exactly did).
I do know of others who have used different partion programs and have had a successful time with it.
I always take great care with partitioning my drives when setting up the OS the first time so that I won't have the need to use programs such as these.