I have a PowerBook G4 867 MHz Processor, 640 MB DDR SDRAM. I'm currently running OS X 10.3.9 and thinking about upgrading to 10.4.9. Is anyone aware of possible issues due to this upgrade? Will the scroll function be possible on the trackpad after upgrade? (there's no such function on the machine currently). Will the applications run as well? Will the overall speed of the machine be compromised or improved? Are there any secrets to know before and after upgrading? I appreciate any opinions. Chris.