How to Reset Blackberry 8520 to Factory Setting

 Without Pc you Can do this :
Erasing the data with the Wipe Handheld option
Go to Options.
Then go to Security.
Then go to General Security.
Click the trackball and choose Wipe Handheld.
Then choose Continue.
Then type blackberry and all of the data should be erased.

 To Using PC connection you can do this

Erasing the data and applications
First connect to Desktop Manager on your comptuer.