Linux is a free operating system, and it has many advantages of windows xp, but it also has some disadvantages. Virtually everything for linux is free, including linux itself. You can install linux onto a computer withought overwriting windows, if you want to try it. You can just download it and burn it to a CD. You may want to try Ubuntu, its good for beginners and it also satisfies the intermediate users. I like it, some hate it, it's up to you.
http://www.ubuntulinux.org http://www.distrowatch.com