So after reading a hundred million (maybe two or three less) messages on this topic, only confusion remains in my head. So here is a simple question for Mac experts: I have an Early 2008 MBP (penryn, model MBP 4.1) which I think is capable of rebooting in 64 bit kernel mode. I have 4 Gb RAM memory and a 2.4 GHz C2D processor. WOULD I SEE ANY DIFFERENCE AT ALL IN MY COMPUTER BETWEEN 32-BIT AND 64-BIT KERNEL? It's easy, I guess. Thanks for answering in advance.