Generally if you access Data Sources from Control panel on 64-bit OS machine it will open up 64 bit Odbcad.exe which might not be compatible with 32-bit DBs. So if you want to create DSN for 32-bit DB you can use below path to locate Odbcad32.exe.
%systemdrive%\Windows\SysWoW64
One best example of 32-bit DSN name requirement is for Teradata DB.
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