I have a 2000 Power Mac G4. The last couple of months it's been running REALLY slow - all applications are slow - internet, Photoshop, etc. At this point, is it worth it to buy more RAM? Will that even help? Also, I have 19 GIGS, but it's showing me I only have 890 MB available. What is so big? What could be taking up so much space. Please! Anyone who can help, please respond back!!!!!!