I am still a happy user of my Aluminum MacBook 2008 (non-pro) and it is running OSX 10.5, Leopard. The CPU is Intel Core 2 Duo. I ran "uname -a" in the terminal and determined that I am running a 32-bit version based on this: Darwin Kernel Version 9.8.0: Wed Jul 15 16:55:01 PDT 2009; root:xnu-1228.15.4~1/RELEASE_I386 i386 If I upgrade to 10.6, Snow Leopard (or any other newer OS) will it convert to the 64-bit version? Do you guys think it is worth it to upgrade to Snow Leopard? Should I consider Mountain Lion as well? Is there an economical way to do all the upgrades?