In order to clear every setting in your Blackberry device and set it back to the factory defaults, you must do a hard 
reset to the phone. A guide for how to do a hard reset for your Blackberry device is provided in the following section.
For doing a hard reset, you must reset the Blackberry device from the software menu. It could be different for each device, but this is a typical reset option that can be performed:
1. Go to Options then Security page
2. Click Wheel, select wipe handheld, then continue
If you now be prompted to input a word on the screen, try to type ‘blackberry’ to begin wiping your phone device. Please take a back up of all your data before doing a hard reset since it will erase all data stored.
How to Guide: Do a Hard Reset for the Blackberry continued »
