Do you want to run Windows 7 on your computer? The Technicist has an easy guide to dual booting that'll let you do just that.
Their guide is for a netbook, but it'll pretty much work on any computer if you just want a taste of Windows 7. All you need is the Windows 7 DVD image, a disc imaging program (I like Daemon tools), a 4GB USB drive (or any external hard drive with more than 4GB) and your computer—though a second, optional flash drive is useful. Then just follow their guide, and you'll be up and running Windows 7 in no time.