You get [Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified on 64-bit Windows

Symptom:

When you try to connect to an SQL Server on Windows 2008 64-bit server running 32-bit application you get the following error

[Microsoft][ODBC Driver Manager] Data source name not found and no default driver specified

And you cannot also find the DSN in the list of ODBC DSNs

Cause:

You must configure the 32-bit ODBC driver. You have been configuring the 64-bit ODBC driver all along. This is not very clear to you (or me), and there is no explicit control panel items for both.

To start a 32-bit ODBC driver,

C:\Windows\SysWOW64\odbcad32.exe