Powermac isnt a laptop is it? I dont know much about previous apple designs.
If its a desktop midtower, I'd go for a WD 640gb drive. 2 platters, quiet, cool, and now fairly cheap. Usually can be had for ~ $70 iirc.
I also have a Seagate 500gb drive in a ziplock bag in my freezer. I'm going to try to grab a few things off of it tonight and you can have it after that, no charge