On the heels of and in the same light as what Dave has last said...
A retail box of Windows 7 offers 2 discs, 32 & 64, either can be used, free choice. As System Builders, using OEM discs we get one or the other, not both. I always go with & recommend x64 when building new machines or rebuilding machines for clients. I am always nudging, advising & pointing towards x64. Certainly, this is based on technical superiority, including lending itself better to future expansion (RAM & more) & more demanding tasking but, largely, as I stated earlier, because it IS the future. For all intents & purposes, x86 is tail-lights & dust, on its last legs. In other words, w/ the pace & direction of IT evolvement, going w/ 32-bit, @ this point in (computing) time, is not prudent, makes no sense. To be future-ready, cutting edge, in step w/ the platforms that are coming & going... x64 is the wise choice.
Regards,
Drew