I just purchased a new 20" iMac and then upgraded it to 4gb of memory. I have the older sticks that are 1gb each. My aging 1.8Mhz macbook pro only has 1Gb of ram and I need to upgrade to 2Gb max as I need to load Leopard. Can I put the 6400S imac memory into my Mac Book Pro that states speed at 5300? Thanks in advance.