Its easy to create a live cd( unless you cannot get one)
1)Download the *.iso* file (Cd image) for the distro you want
2)Wait....this is step 1....select a good distro
3)Burn it (not your pc, the image onto a cd!)
4)Now go to the bios and select cd rom as 1st boot device, insert cd and boot.
This will run on the ram and will not make any changes to your system.