Cleaning the Mac

After getting my nice shiny MacBook fixed, I'm pretty confident that it's not going to break again. So, I've decided to get rid of my old iBook G4 by cleaning it up and giving it to my parents. I have all the software they would need for it, and I would install it and register it all for them, but first I'd like to erase the hard drive so that they can start fresh.

I'm a bit of a newbie at this- has anyone had any experience with refurbishing an old iBook? How did you do it? What should I watch out for?

Thanks!