Things have changed a few times since my original answer. 64bit prefixes versions of Wine are pretty capable these days. I haven't had a pure 32bit version in at least a few years.

Your "Wine prefix" (traditionally at ~/.wine/, but settable via env WINEPREFIX) controls how things will be run for the lifetime of that prefix. If you set up a 32bit prefix, everything will run in 32bit mode in that prefix. Conversely, if you don't do anything and run anything special, you'll create a Wine64 environment.

If you're starting a new prefix (ie on a new install of Ubuntu), you'll need to do a few special things:

# Move the old prefix (if one exists)

# You could rm -rf it if you don't want it.

mv ~/.wine/ ~/oldwine/



# Create prefix with right arch, per

# http://wiki.winehq.org/FAQ#32_bit_wineprefix

WINEARCH=win32 winecfg

And that's it. Unless you're specifying another prefix that doesn't exist yet, you shouldn't need to set WINEARCH again.

The revision history to this answer holds additional information that I don't think is relevant in 2018. This is mostly point and shoot these days.