It's all very well expounding the virtues of Linux, but there's a big barrier to entry. Linux is complicated, PCs are complicated, and if someone's got a working computer then they're obviously reluctant to start tinkering with the insides. They don't want to completely abandon their Microsoft-based system and their functioning applications while they figure out what Linux is all about.
Of course you can set up the machine in a dual-boot system, so the Windows stuff remains, the Linux gets installed as well, and then a boot loader is added to let you select which one you want to use. But that means partitioning the hard drive, and tinkering with the booting process, and that sounds risky. What happens if it goes wrong and then Windows won't work any more? Is it possible to repartition the hard drive without losing the Windows applications - or worse, all that personal data?
This is where the live Linux systems come into their own. There are several of them around (see the Linux distributions page), but the most popular is currently Knoppix and that's what we're playing with here. The massive advantage of systems like these is that the whole thing, the Linux kernel, the window systems, even all the applications like graphics packages, word processors, spreadsheets and browsers, all fits on a single CD!
With one of these CDs, you don't have to install anything on your hard drive, and you don't have to repartition or reinstall or reconfigure the boot manager or anything like that. Just boot from the CD if you want to, or take the CD out and boot from your hard drive exactly as you did before. In this way you can experiment, and get the hang of things, without risking your hard drive.
On the one hand, the fact that you're booting from CD seems like a disadvantage - if you change your settings or preferences, they'll be gone next time you boot up. But this is what makes it great for experimenting - if you do something drastic and the system stops working, you can boot from fresh next time without fear of having broken everything. And, as we'll see, there are ways to store settings and files for use next time.
Of course, Knoppix isn't the only live distribution, and there are plenty of others to choose from. These give you a chance to see other systems, with other applications, other ideas and different look-and-feels, without risking an install. If you like what you try out, you can maybe bring those ideas together in your full, installed system.
A selection of other distributions are examined in the live distros section, including Ubuntu, Enlightenment-based Elive, Xfce-based Xubuntu and also KDE-based Mandriva One.