Want to try out Linux? Check out Ubuntu, a Debian based distro that allows you to run Linux without changing anything on your computer. If you like the way it works, you can then install it to your hard drive and create a dual-boot system, so you can still use your original operating system. You will need to download an ISO image and write it to a CD, then you can use the CD to boot into Ubuntu. Ubuntu is designed for the average computer user, and as such you don't need to be an expert to install it. Ubuntu versions exist for both Intel/AMD personal computers, as well as Apple Macintosh computers.
If you are a free software purist, you may want to try Ututo GNU/Linux. Ututo contains nothing but free and open software.
Have fun!