Erasing all data on a BlackBerry

Erase all the data on your handheld

  1. On the handheld, click the Options icon.

  2. In the Options screen, click Security.

  3. Click the trackwheel and select Wipe Handheld.

  4. Click Continue.

  5. Type BlackBerry. All the data on the handheld is erased.

Erase all the data and applications on your handheld:

  1. Connect your handheld to the personal computer running Desktop Manager.

  2. In Desktop Manager, double-click the Application Loader icon.

  3. In the Application Loader Wizard window, click Next.

  4. On the Handheld Security Password screen, type an incorrect password and click Next.

  5. Repeat step 4 ten times. The handheld resets. This might take several minutes.

Reference: http://www.BlackBerrycool.com/2005/10/erasing-all-data-on-handheld/