Here is a description of a Linux distribution known as Knoppix, from Germany.
I have used Linux from its earliest days when I got it on a set of some 20 floppy disks from a local dial up Bulletin Board. It required enormous patience and not a little luck to install and configure at a time when computers were nowhere near as inexpensive as they are now.

Knoppix is another flavor of Linux, with a twist it shares with only 2 other of the many distributions I am aware of- It easily launches and initialises from a CDROM WITHOUT installing itself to the hard drive.
You launch it– it works. That's It. At least on most modern hardware. 

Plus, its Free.
You will need a high speed connection or freinds with one,
and the ability to burn CDROms, then visit here: http://www.knoppix.com  

If you are Nice to us we can probably get you a copy, and Yes, it is legitimate to copy and redistroubute this just as much as you like.

THsi CD makes a superb testing utility for a machine where you are uncertain whether Windows is broken or there is somethign wrong wotht he hardware, as the CDROM boot sequence checks everythign thoroughly. Plus, there is an override taht allows you to perform a so called MEMTEST86 Memory Check for those more elusive troubles. These are all things it is almost impossibel to check whilest inside Windows itself.

 How easy is Knoppix to use? you be the judge. We welcome your reviews here..!