I have a Macbook (spring 2006) and got sick of the beachball all the time and decided to upgrade from my 512. I ordered the correct type of RAM, 2x1GB. When I installed them, one was DOA but the other worked so I ran my computer with 1GB+256MB until the replacement arrived. The new 1GB arrived yesterday and when I changed it out with the 256 to have 2x1GB the computer wouldn't boot...not even the chime. I tried the various suggestions in my user guide with no luck. When I tried to go back to the 1GB (original on that had been working for a week or two) plus then 256, it would only recognize the 256 (had to use power + D with the CD that came with my mac to find that out). Turns out the only way I can get my computer to run is with the orginal 512! Needless to say I'm frustrated and not enjoying being back to 512 with the beachball! Can anyone help?