Absolutely...I run 10.4.2 on my old Sawtooth 400 Mhz G4 which I use as a web server, while I do my graphic production work on my Dual G5. It definitely helps if you have your RAM slots maxed out. I have 1GB in mine and the beachball still spins sometimes. OSX 10.4.2. is a bit of a RAM hog.