if you get a winetricks error like:

wine cmd.exe /c echo '%ProgramFiles%' returned a string containing the word 'unknown', as if a voice had cried out in terror, and was suddenly silenced.

Fix: backup existing system.reg file by typing in Terminal:

cp ~/.wine/system.reg ~/.wine/system.reg.bak

Use text editor and “replace all”

C:\\windows\\system32\\unknown

with

C:\\Program Files