Open the NetUpdate application as illustrated here and the software will automatically check for updates. Once this process has completed, click OK. Next, hold down the Optin/Alt key on your keyboard, click the NetUpdate menu located in the upper left corner of the screen, and choose "Reset Preferences...":
Click Reset to erase the current e-mail address:
This will cause NetUpdate to close. Now, relaunch the program from your Applications folder, or from the Intego 'tower icon' in the top menu bar. You should now see the following:
Select 'Open' and it will launch the NetUpdate Preferences window:
Enter the new e-mail address and press the Return (Enter) key and your new e-mail address will be stored.