I wanted to put my 2.5ghz's MBP's 1gb chips into a friend's 1.83ghz core duo macbook. When I pulled one of the chips out of the macbook it didn't 'click' as it unlocked. I didn't think anything of it until I couldn't get the 1gb to lock into the slot. Or either of the original 256mb chips. They'll slide in but the computer won't boot with a chip in that slot. It works just fine with a 1gb chip in the second slot so she does have twice as much ram as before the evening started. My questions are: Is 1gb in a single chip better than 2x256mb? Not certain how this dual channel ram works. Is there any chance that there is a simple way to get the first slot to work again? (She didn't buy the extended warranty so any repairs are on my dime. I don't 'think' I did anything to cause the problem, but it worked before I took the battery out.) The chip that came out of that slot was white on the leading edge of the contacts. Any ideas as to why/what that might be and if it could be connected to the slot not working any more?