Spread the word about this absolutely brilliant distribution! If you have high speed internet, download now, if not, get the CD. It is soooooo worth it. I've been handing them out like candy here, and everyone has been extremely impressed (old Windows users are being turned). No install. It is installed on the CD, and won't mess with your HD unless you really want it to. Comes with great software, some nice programming environments, etc... Completely safe way to "play" with Linux (until you realise you can't live without it and trash your other OS).
edit: Just worth reiterating: it doesn't use your hard drive at all, not for temp files or anything. Not unless you specifically set it up to (which you really can't do on accident).