My office is ditching a lot of old gear and I inherited a Power Mac G4 AGP, 500Mhz model. It's currently running OS X 10.2.9. Now I'm not all that Mac-savvy, I grabbed it to learn (and it's free, after all). So, what can I do to upgrade this puppy? I see it uses PC100 memory, can I use any memory? Also, will any AGP card work? What about a processor or HD upgrade? All help (and patience) is appreciated.