Even on a 64-bit Windows 7 machine, 32-bit apps (like some older versions of MS Office) require the x86 version of the driver.
Click and select PostgreSQL Unicode (recommended for better character support). Fill in the connection details: postgre odbc driver windows 7
If you're looking for alternative ODBC drivers for PostgreSQL on Windows 7, consider: Even on a 64-bit Windows 7 machine, 32-bit