System DSNs are stored in the registry. If you manually make the change on one machine, then export
the registry key to a .REG file, you can distribute that file to all users. With a simple script
you can have the reg file executed on each user's machine. Of course, there are several other
options, but this one is pretty simple.
The registry key is under HKEY_LOCAL_MACHINE\SOFTWARE\ODBC\ODBC.INI