I've been playing alpha for about 3 months now, and this is the second time that my minecraft level data has been completely erased. I was working on something incredible too, and all of that effort has gone down the drain.

So my question is this: Is there a way to copy/backup minecraft levels in single player in the case of lost data or system crashes? I've searched the forums for topics about it, but I must be using the wrong words since queries including the words "copy" and "backup" yield no results.

Please help, and thanks in advance.