The 16MB graphics and 32MB graphics G3 iBook's were the software over clockable machines, I don't think it will work for yours. It's not OS X that is sucking up all that. Check over your files. Do you really need all of them? if not get rid of some and put them on another machine or external hard drive. Leopard might be better at some things and lack in others. It's it and miss I believe. I use Onyx to get rid of uneeded OS X files. You do not have to do any digging with Onyx, it's all auto.