In order to hard reset a BlackBerry Bold 9790, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
BlackBerry Bold 9790 device will be brought back to the default configuration of a brand new device.
1. Power up the phone by pressing the Power button.
2. Next, open Main Menu by press-holding the Memory Key.
3. Choose Settings, then Security Options and then Security Wipe.
4. When prompted to, type the word "BlackBerry" into the phone.
5. The last thing to do is to begin the security wipe. Do that by tapping the Wipe option.
6. Woohoo, the hard reset is complete. Pat yourself on the back and open up a bottle of beer.