To reset your Blackberry to the factory settings:
1. From your applications list, click on Options.
2. Click Security Options.
3. Click Security Wipe.
4. Perform any of the following actions:
• To delete data from the messages application, contacts application, and other applications, select the Emails, Contacts, Etc check box.
• To delete all third-party applications that you have added, select the User Installed Applications check box.
• To delete all files from your media card, select the Media Card check box.
5. Type blackberry.
6. Click Wipe.
You may also click here to view an article from the Blackberry website on how to reset your phone.
Hope this helps!