'alstein',
Given that there is 4G RAM the answer is, pardon me, no offence meant, a "no brainer"... go 64!! It is worth it.
If you would like me to elaborate I'm willing but, comes down to, if you can do it, do it, no hesitation.
I run XP & Vista x86 & Windows 7 x86 & x64... go 64, absolutely. Or both, 32 & 64 if... (hardware issues)
Cheers,
Drew