Confused? Good. You're not alone. Microsoft is a bit confused as well.
If you happen to be running Windows 7 64-bit and you haven't looked at PowerShell yet, you may be a little surprised to see there are two sets of shortcuts on the "Start" menu. One set for x86 and the other for x64 (unlabeled). So, what's the difference? Aside from how each is managed in the Windows memory and process stack environments, they do behave differently. I haven't begun to map out all of the possible deviations betwixt the two (I never get to use the word "betwixt", but now I can! moo-ha-ha-haaaa!), however, I have run into one in-the-face obvious difference:
ENVIRONMENT variables on 64-bit Windows
If you open each console (yes, you can run them both at the same time), and type the following statement in and hit Enter, you may notice the output results are not the same:
Here's a screen shot of each:
I highlighted the key differences in red for the visually and mentally impaired (like me). Can you spot them? Have you played "Where's Waldo?" I have to pause for a second to say that "x86" is a stupid-ass name. Why not "x32"? The "x64" is still based in large part on the "x86" architecture, so maybe they should be "x86/32" and "x86/64"? Whatever. I'm on my third beer, so I really don't care. It's all stupid. And making two versions of the same script interpretor on the same operating system is also stupid as shit and makes no sense at all. Why even make a 32-bit version on a 64-bit machine? Is there a 64-bit version of VBScript? CMD? Explorer? Feh.
So, basically, if you're writing PowerShell scripts that will run on 64-bit clients, be careful to test the differences before unleashing it in production.