How to reset BlackBerry Curve 8900. there are two ways to reset BlackBerry Curve 8900:Soft/Hard Reset and Master Reset (Wipe Handheld). but there are difference between them.
BlackBerry Curve 8900 Soft/Hard Reset : Alternatively press and hold ALT + CAP + Delete to perform a reset. (NOTE: A soft/hard reset will not result in data loss.)
Press the release button and slide off the battery cover > Remove the battery from the BlackBerry> re-insert the battery. ( NOTE: Reinsert the battery so that the BlackBerry logo faces up and the metal contacts on the battery align with the metal contacts on the BlackBerry.)
BlackBerry Curve 8900 Master Reset (Wipe Handheld)
In the blackberry menu go to Options > Security Options > General Settings and select Wipe Handheld.
The device is going to confirm that the data will be erased. Select Continue.
(WARNING: A master reset will result in the loss of ALL user data! It is recommended to perform a backup of the RIM BlackBerry data)