Yes Leopard can run 64 bit applications, and you have 64 bit processor.
That doesn't mean Safari is a 64 bit app though. Leopard can run both 64 and 32 bit process seamlessly.
Very few applications out there would see any benefit from being 64 bit (only applications that need to access massive amounts of data).
The only application that I know of that is included with Leopard that is 64 bit is "Chess.app".
From what I gather it lets your computer work with files larger than 4GBs much faster because it can load the whole thing into the RAM, or something like that...
From what I gather it lets your computer work with files larger than 4GBs much faster because it can load the whole thing into the RAM, or something like that...
Wrong and wrong. 64 bits means that the registers are 64 bits wide, so it can use larger numbers and address a larger memory base. It might even be slower then a 32 bit CPU as the address pointers to the memory take longer to process. Larger numbers does not automatically mean faster.