Ubuntu Live CD
Ubuntu Linux is available freely at http://www.ubuntu.com as a download. Once you download the .iso file and burn it to a CD, you can use it right away. With the CD in the drive, reboot your computer. You'll be greeted with a screen that asks you if you want to try out Ubuntu or install it on your computer. To use it as a Live CD, select "Try Ubuntu".
When it is done booting, you'll have a complete operating system at your disposal. Under "Applications" in the upper left hand corner, you'll find OpenOffice Writer and Calc, Mozilla.org's Firefox web browser, and a number of other programs.
This live CD is great for starting up your computer when children or grand children want to play on the computer. Its next to impossible for them to do anything that will harm your computer. It is also nearly impossible to get a virus that will cause problems.
You will also see an option to install Ubuntu. You can install it instead of Windows, or you can make the computer be able to boot either Windows or Ubuntu.
Lastly, Ubuntu runs great on older systems. If you have a computer taking up room in the closet or garage because it is just too slow, try installing Ubuntu on it. You will likely be surprised to see that your old computer is now a useful member of the household again.