XP 64? use or not

Building some computers for my friend and it just hit us we might need 64.

specs are intel core2 quad, p5e asus, 8600gt, with 4(1x4) gigs of ram.

these are for rendering with maya mainly and ive never had a need for 64 with my own computers. should i download, i mean buy, 64 or stick with oldschool xp

>>11
In practice, you aren't going to be reading from disk continually when you're doing shit, but from RAM and cache memory. Vista is an exception because it expands to occupy all available RAM, so it *will* be swapping to disk all the time, but you aren't running Vista.

And this isn't the 1960s anymore. Compiler theory has come a long way, and there are very good optimising compilers out there. If anything, hand optimisations are to be avoided because compilers don't generally touch assembly code itself.
Generally speaking, if your code is compiled for a 64-bit system, it will take advantages of the architecture more than adequately, and almost always far better than a human programmer could hand-optimise it, especially for really large projects like OSes.