/private/var/db/SystemConfiguration/preferences.xmlTo get at it, open a terminal window and enter the following command:
% open /private/var/db/SystemConfiguration/The folder should pop open in the Finder, displaying (at least) the preferences.xml file. Drag it out of the SystemConfiguration folder to your desired location to back it up. It should make a copy, not move itself, as indicated by the "plus" sign that appears beside the cursor when dragging it out of the folder; if a "plus" sign doesn't appear, hold down "Option" key as you drag it to force a copy. You should not need root privileges to copy the file, as all users have read access to it.
To reinstall it on your freshly installed OS X, you will have to use the Terminal and use the "mv" command with root power, ie:
% sudo mv (backup/file/path/)prefereces.xml \Wish I would've known this before I reinstalled my OS thinking my "pay as you go" internet service providers password and login info was safe in my backed up Users folders. Would've saved me time re-configuring my 15 different locations too!
/private/var/db/SystemConfiguration/

