Well 32bit windows would be enough for most people if Microsoft fixed 4gb issue. 32bit Os is capable to address up to 64GB of memory but max memory per allocation is 4gb. In linux that is solved with highmem option but it windows it just doesn't work like it supposed to. Vista x64 works fine but lack of drivers is the reason why people are not migrating to XP or Vista.
So I can agree with AuDioFreaK39 until in this case 32bit version of windows exist companies will mainly focus on 32bit drivers and they will neglect x64.
Interesing - and how might an x86 OS be capable of addressing up to 64GB of memory? I've never heard this before.
On linux u can enable in kernel two options, if i remember correctly by default linux sees only 1GB or 2GB:
HIGHMEM solution for using up to 4 GB of memory
HIGHMEM solution for using up to 64 GB of memory
HIGHMEM solution for using 64 GB of memory
This is enabled via the PAE (Physical Address Extension) extension of the PentiumPro processors. PAE addresses the 4 GB physical memory limitation and is seen as Intel's answer to AMD 64-bit and AMD x86-64. PAE allows processors to access physical memory up to 64 GB (36 bits of address bus). However, since the virtual address space is just 32 bits wide, each process can't grow beyond 4 GB. The mechanism used to access memory from 4 GB to 64 GB is essentially the same as that of accessing the 1 GB - 4 GB RAM.
Ignore that part about AMD 64-bit and Pentium PRO. Anyway there are ways to fix it, and until Vista came out we were stuck with Windows XP x64 which wasn't even supported by MS and most companies didn't released drivers.