I put a Seagate 5400.3 (160GB, 5400rpm, perpendicular) in my 1.25GHz PowerBook and I'd say it feels like a 20% increase in performance. It's dead silent (in a good way 😉 ) and no heat issues. Add the 5 year warranty to boot! I have nothing but good things to say about NewEgg by the way...that is where I got mine over a year ago! I installed it myself - not too hard for someone comfortable with hardware. If not you, perhaps a friend?