Is there such a thing as 32-bit Windows 8.1? Or a compatibility mode that runs 32-bit on the 64-bit machine? I guess I am confused about whether 32/64 bit is a hardware thing or a software thing. It was my impression that it is strictly hardware, so I have no possible USB option with this computer.
Tom already answered this question for you from a practical standpoint. But I thought you might like more clarity on this one:
In Windows 8, go to your system information screen. Either navigate the Windows Control Panel and search for System, or, move your mouse pointer to the top-right edge of the screen so that the "charms bar" appears, and then select "Settings" and then select "PC Info". You should see a screen like the one in the attached screenshot.
Notice how it says, in the highlighted area, that it's a 64-bit operating system running on 64-bit hardware?
You could, if you wanted, format your hard disk and re-install a 32-bit version of Windows from scratch. Then that screen would say that it was a 32-bit operating system running on 64-bit hardware. That would work. But then, as Tom said, the OS wouldn't be able to make use of the extra RAM installed in your system. There are also other advantages to having the 64-bit OS running. So you don't want to do that.