I don't know how people choose their OS from but for me I choose Windows Vista 32-bit for my primary machine. Why? You'll know from the listing below--important thing always comes first.

  1. Software compatibility -- this is the biggest issue of me since the first day Office 2007 arrived, I found myself stay away from Linux or any other OS more and more. It's not about the ribbon tab interface, but only one program in 2007 suite. Many of you guys may know now. It's OneNote 2007. Dude, that's an awesome piece of software on the earth. It makes Windows distinguish from others indeed, at least for me. That's only a few programs that are not cross-platform I use but now I can't live without it.
  2. Hardware compatibility -- If you buy something on the street but can't use it, it's a problem, isn't it? who will argue me about this? drivers for Linux, yes they are better but, as long as reality is concerned, they are out of Microsoft's league. Mac OS, huh? don't even think of this. Talking about 64-bit hardware, since AMD released its first 64-bit CPU around 2003 (5 years ago), now they might realize that they have made a huge mistake having backward-compatible with 32-bit instructions. That's what Intel followed and has made the world still doesn't care about 64-bit much because 32-bit system still is working very well. 64-bit system is great--fast, nice but you can't just simply pop some old cards into 64-bit system.
  3. Friends -- this also is a big factor. If you are only one using Mac in your workplace and are not tech savvy, you'll know what I mean. I do think of myself in that situation; I would argue that I can do everything Windows people can, but for docx, xlsx, pptx file I would have no idea what folks around talking about for a year, then I realize it's new version of office suite file and can open them. You can't just always let anybody save in backward compatible type.

From all 3 factors above, choices will come down to 2 which are Windows 32-bit & 64-bit. For friend factor, they look alike & work the same, so nothing to worry about. For hardware compatibility issue, they are almost on par for both systems nowadays (if you don't have such a rare item, you won't find any trouble with 64-bit anyway) However, the problem comes down to software compatibility. You still have to use 32-bit browser to watch flash contents; you still have to use many 32-bit software. Although they are running flawlessly under 64bit system, one thing I found it wouldn't work is OneNote. They are no OneNote virtual printer for 64-bit system. It's just a deal breaker to me. Yet there is no one to blame since we all are okay embrace older system while we all already have newer stuff around. That's just why we haven't had a big step forward. I mean 64-bit system is getting better and better now but if you have to put more effort to get things work and result are the same, why wouldn't we go easier route for now? Then when things have changed, so can we. This is how and why I choose 32-bit Windows as my main operating system.