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Using the macbook go to:

www.crucial.com

on the left press "scan my system"

it will show you the exact details of the RAM you need, plus some average prices. Macbooks can be funny, because even if you think you have chosen the right RAM, it usually doesn't work because it isn't Apple verified. So doing the steps above will show you exactly what you need.

Crucial is good, but a little expensive, so i wouldnt buy from them
 
This is a G4 Powerbook 15" last generation, not a MacBook Pro.

Ram is backwards compatible, but thanks for the crucial link, they have this memory for five bucks more than newegg and it is verified for last gen Powerbooks that take ddr2 instead of regular ddr ram.
 
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