I have just bought a brand new MacBook Pro with 4 GB RAM, and was wondering which Windows 7 version 32 bit or 64 bit I should install with BootCamp, in order to do Visual Studio development? 

Is Visual Studio 32 bit? Any pointers to the correct install process would also be appreciated.
['https://superuser.com/questions/58913', 'https://superuser.com', 'https://superuser.com/users/-1/']
While Visual Studio is 32 bit application, depending on what type of applications you're planning to develop, you might find it beneficial to use the 64-bit version. IIRC you can run and debug both 32-bit and 64-bit executables in 64-bit Windows but not in 32-bit Windows (as the latter isn't able to run 64-bit apps).
Visual Studio is a 32 bit application only, so if that is the major reason for installing windows, 64-bit will not give you any additional features, other than it will be able to handle all 4 GB of memory, whereas 32-bit will only give 3.2 GB or so.

See this question for details about general 32-bit vs 64 bit systems: 

* [32-bit vs 64-bit systems](https://superuser.com/questions/56540/32-bit-vs-64-bit-systems)