The Natural Philosopher wrote
Richard Russell wrote
Jim Hawkins wrote

When I get a new PC it'll be Windows 7, but what are the pros and cons of the two different bit sizes ?

Pros of 64-bit Windows 7:

1. Can run genuine 64-bit applications (but there are very few of those).

2. Can support a larger amount of physical memory (maximum 4 GB on Win32, up to 192 GB on Win64 depending on
version).

Cons of 64-bit Windows 7:

1. Can't run any 16-bit (DOS) programs - other than using a emulator
like DOSBOX.

2. Poorer support for legacy device drivers: if you have an older
scanner, printer, camera etc. 64-bit drivers may not be available.

3. 32-bit applications run under the WoW64 emulation layer:
compatibility is good but not 100% and a few programs may not run properly.

On balance I generally recommend the 32-bit version, but YMMV.

compare and contrast with Linux/Mac OSX where "on balance I generally
recommend the 32-bit version" became the reverse about three years ago.

Just as true for many with 64bit Win7.

And it has the advantage of a lot more commercial apps available for it too.