Upgrading RAM on old MacBook I need to upgrade the ram on an old macbook. It takes DDR2-667Mhz. Although those are quite expensive (guess they are not made anymore?). If I get higher MHz DDR2 memory will it still be compatible and just run at 667? Are there chances that it won't work? Also what about 1067 DDR3?
DDR3 ram is not pin compatible with DDR2 so you will have to find the DDR2.

The higher speed RAM should work as it throttles down to the speed that the motherboard can handle.