P5N32SLI and 64-bit

Hi... confused here.... I'm building a new Pc with the above mobo as the
backbone. I was going to put an E6600 CPU in it. Running XP Pro.... as
Vista is poop.

Anyhoo... suddenly got me thinking about 64-bit in general i.e. 64-bit XP,
and a 64-bit processor? But then do I need 64-bit memory. The way I was
thinking was based on the memory restriction on 32-bit XP i.e. 4GB max.

Am I thinking right? Can I go to 64-bit with the mobo? Is it worth it?
Running XP 64-bit... with a possible requirement for diff. memory? I would
like to run more than 4GB.

Hope that all made sense.