What's so great about Knoppix?

I'm just wondering, because I keep hearing about it and I've read a little bit about it. From what I understand it's just an OS that runs off of a CD. A version of GNU/Linux, I guess.

So what makes it worthwhile? I mean, can you write data with it? Because it's on a CD...

Anyways, I'm a total newb when it comes to Linux and this Knoppix thing has been bugging me for a while.

WHAT MAKES IT SPECIAL!?

Something about it coudln't find the file system. Don't ask me; as I said it only gives me this error on the newer desktop. I fail to see why there should be a problem with the file system especially when I burnt the thing directly from the ISO.

I do have a quad-core; could the processor type be what's wrong? As for Ubuntu, I tried it, and sorry, it's just not working out. Turns out I have to use an entire hard drive rather than a small partion of it. While I could always back everything up, it's just more hassel than it should be. That...and a Live-CD is good to have on hand as a last resort.