This weekend I upgraded my 250GB hard drive to a 500GB hard drive in my main computer. I’ve done this countless times with little effort but this experience was anything but pleasant.

I’ve mentioned GParted before as an excellent free partition manager.  HowToForge.com has posted an excellent walk through to get the hesitant started.
Modify your partitions with GParted without losing data

While this is written for Linux the creators of GParted have a Live CD version that works very well.  I suggest you know what you’re doing with partitions before you get into this, but GParted does everything you would need to do for hard drive partitioning, without buying Partition Magic.
Gnome Partition Editor