If you want to "play" with Linux, a better option is to use a Live CD or DVD. Most Linux vendors offer them as a free download, you can burn the ISO to a CD or DVD and it will run Linux as normal from the drive. This way you don't have to reformat your hard drive until you get familiar and also see which Linux Distribution you like best. Here is a site that offers alot of different linux distributions, many are live versions. Linux ISO's The name should specify Live for it to be a Live version, not all offer it.
If you decide that you want to install a distribution, then Partition Magic is probably the best non-destructive method. The best is to start from scratch though. Some of these distributions will squeeze the partition down and install on the free space if you ask it to. I am not familiar with which ones do this and I also question the stability of doing this.
Out of the distros I like Suse for ease of use.