Any info is appreciated..... I have a 15" 1.5GHz Powerbook G4. In system profiler it said my upper memory slot had a 512mb stick and the lower slot was empty. I ordered a 1gig stick, opened up the back and the lower slot actually had a 256mb card in it already. I went ahead and switched the 1Gig for it. When I turned my computer back on it took an unusually long amount of time. Now it says the lower slot is still empty, but still reads the 512 in the upper slot. Thoughts? Next I'm going to switch the places of the 1gb and 512mb sticks. maybe i just have a faulty slot.