Which Windows 7 to install?

The Windows 7 system requirements declares 2GB as minimum for 64-bit.
Going by earlier system requirement statements from Microsoft, I would suggest using 32-bit.

If you are attracted to 64-bit (I do not see a reason for that in recent times)
You could upgrade your memory and start with the 64-bit edition.


Other references.

  1. Gizmodo: Why You Should Go 64-Bit With Windows 7
    • If you're not planning on going to 4GB of RAM anytime soon, you might wanna hold back, since you need 4GB of RAM to take full advantage of 64-bit's memory management. That said, RAM is so disgustingly cheap right now, and has such an intense bang-to-buck ratio, you should definitely upgrade to 4GB if you haven't already. Anyone who runs specialized or older gear should probably not jump into 64-bit.
    • Windows7 Forums: Windows 7: 64 bit vs 32 bit? -- 64 bit pro and cons
    • You can address much more than 4GB of memory [whole idea is, handle more memory]
    • 16 bit applications will no longer run
    • Existing 32 bit drivers no longer work
    • Unsigned kernel-mode drivers no longer work
    • Running some 32 bit applications on a 64 bit OS could actually be slower
    • The Microsoft 32-bit and 64-bit Windows FAQ
    • linked from Windows 7 features, 64-bit support page

I don't think there's a black and white answer here, there are pros and cons for both:

32 bit: Pros

  • Better device driver support
  • More 32bit applications

64 bit:

  • Larger available memory space if you have more than 3Gb RAM
  • All compatible device drivers are signed

In your case with only 2Gb ram I'd probably just go 32bit as there isn't significant benefit going to 64bit.