Sprint Nextel SCP-8400 - Manual (Page 106)

90 Section 2C: Setting Your Phone’s Security
Resetting Default Settings
Resetting the default settings restores all the factory defaults,
including the ringer types and display settings. The Contacts,
Call History, Calendar, and Messaging are not affected.
To reset default settings:
1. Select > Settings > Security, and then enter your lock
code. (The Security menu is displayed.)
2. Select Erase/Reset > Default Settings. (A disclaimer
appears.)
3. Read the disclaimer and press OK (left softkey).
4. If you are certain that you would like to restore all of the
factory settings, select Yes.