If you are troubleshooting ODBC issues on machines running 64-bit operating systems (especially with 32bit apps) then you may need to check the 32bit version of ODBC Data Source Administrator.
The 32-bit version of the ODBC Administrator tool displays 32-bit system DSNs, 32-bit user DSNs, and 64-bit user DSNs. The 64-bit version of the ODBC Administrator tool displays 64-bit system DSNs, 32-bit user DSNs, and 64-bit user DSNs.
Administrative tools –> Data Sources(ODBC) by default shows the 64-bit edition, run the 32-bit edition from C:WindowsSysWOW64odbcad32.exe
The 64-bit edition is located at C:WindowsSystem32odbcad32.exe – indeed a very confusing file naming convention – you must close any open ODBC admin windows first, otherwise you won’t see any changes.
More information from Microsoft –> http://support.microsoft.com/kb/942976/en-us