Most software comes with some sort of key of random characters that needs to be entered to get the software to work. The key is usually on some piece of paper that, without fail, I always manage to lose. After once losing such a key and then needing it later, I can tell you that if you lose this key you are pretty much outta luck. That's why whenever I buy a piece of software, the first thing I do is get a Sharpie marker and write the key directly on the CD/DVD that contains the software. That way, as long as I have the CD/DVD, I'll always have the key I need to use it.