[jexamilotis]

This procedure applies to the Samsung Jack SGH-i637 running WM 6.5. It may work on other phones with this operating system, but I have no way to verify it. Assigning an Unknown Caller ringtone is a backdoor approach which requires editing the phone's Registry. I used Mobile Registry Editor v1.11 which is a free Internet download. It works with both Vista and Windows 7.

Step One:
Decide which ringtones will be used for numbers in the Contact List and Unknown Callers. These can be default ringtones on the phone, or new ones added to: My Stuff\My Documents\My Ringtones

Step Two:
Under 'Settings', select the ringtone which will be used as the Default for Contact List entries. A specific ringtone can still be assigned to individual numbers.

Step Three:
Start the Registry Editor, and navigate to:
HKEY_CURRENT_USER\ControlPanel\Sounds\RingTone0
The values listed are for the Default ringtone selected in Step Two. The following 2 values need to be added to another Registry Key.
Category String Ring
Sound String {%Path to Default Ringtone%}

Step Four:
Move up the navigation pane to the registry key 'KnownCallerRing0', and right click. Highlight 'New', select 'String Value' and add the 2 values found in Step Three. Make sure to enter the Sound String Data exactly as it appears in Step Three. Exit the Registry Editor.

Step Five:
From the phone, go back to 'Settings' and select the ringtone to be used for Unknown Callers. That's it, you're done. Test it by calling your phone from an unknown source.

Remember, from now on when you change the ringtone on the phone it is for Unknown Callers. To change the Contact List default, you have to use the Registry Editor.

To reverse this procedure, delete the 2 values added to the register key 'KnownCallerRing0' and re-select a ringtone under 'Settings' from your phone.