MacOS X 10.6 Snow Leopard is 64-bit - or is it?. Well, actually MacOS X 10.6 Snow Leopard is both 32-bit and 64-bit, and what that means for you depends on both your hardware and your settings.
I put up an accompanying 0 website which should answer most of your questions at
What does this app do?
Thanks for all the feedback - but PLEASE read the website before asking questions. About 500 people must have asked why their Mac is still in 32bit KERNEL mode after applying the settings - and it is explained in detail on the website (I think I got rather grumpy after answering the first 300 mails)