If you have installed a 32-bit ODBC driver on Microsoft Windows x64, such as psqlODBC, you will find that 32-bit ODBC drivers do not appear in the ODBC Data Source Administrator. To resolve this issue, use

%SYSTEMROOT%\SysWOW64\odbcad32.exe

instead of the default program in system32. This will show all installed 32-bit ODBC drivers. At this point you can use your DSN as you would with any other system.