So I've got an iMac G5 iSight (from '05 I think), running OSX Tiger. It has become really slow, and feels like it is "chugging" along when I have multiple Firefox windows open. Never used to have this problem, but after 4 years of use I'm guessing that this is somewhat normal. I'm fairly savvy with these things on the PC, but I'm newer to tackling Mac issues as this is my first problem in 4 years! Disk space isn't the issue, b/c I'm only using 120/250 gigs. Do Macs need the occasional disk/file cleanup/defrag like PC's do? Should I reinstall OSX, or would you all recommend an alternative strategy?