No install required - doesn't make any changes to your Windows installation.

Go to http://www.knoppix.net and click the "Get Knoppix" button. It's a 700 meg download, so hopefully you have a broadband connection.

What you're downloading is an ISO image of a bootable CD. Just about any CD-burning software should be able to burn it to disk, which you can then use to boot your computer into Linux. Just put the CD in your drive and restart the machine. When the login prompt comes up, type in "knoppix" and press ENTER.

Presto! You're now running Linux, complete with a full suite of applications, games, utilities, etc. It should automatically configure most devices including USB. Keep your /home directory and your config on a USB thumb drive and you've got a portable Linux system that will run on pretty much any PC with a CD-ROM and a USB port.

To get back to Windows, log out of Knoppix, remove the CD when prompted, and turn your computer back on. (Knoppix helpfully powers off the machine when you sign off the OS)

It's a great way to get a taste of that real Linux experience without having to make any permanent changes to your computer. And did I mention that it's FREE?