not sure on apple what can be removed and not removed etc. I have a PowerBook G4 w/1.33 GHz, and Ram is as listed. Dimmo/Built-in 256 MB Dimm1/j31 512 MB DDR SDRAM PC2700U-25330 What can I bump this up to and can the built-in be swapped out as well ? I know this may be a really dumb question but it is one i just don't know the answer too. thanks !