If you attempt to use ODBC to run a MySQL application and run into the following error:
[Microsoft][ODBC Driver Manager] The specified DSN contains an architecture mismatch between the Driver and Application
This means there is a 64-bit versus 32-bit mismatch.
Most likely, you're running 64-bit Windows, as well as 64-bit MySQL ODBC connector, but the application is 32-bit.
If this is the case, you will also need to install the 32-bit MySQL ODBC connector, and then create the connection from the 32-bit ODBC.