The factory reset clears all user data and 3rd party applications, restoring the device to it's original factory settings. It's often recommended following a software update to help resolve or clear compatibility issues Prior to performing the reset, it is recommended to backup your personal data (see below) and then remove the SD card.
Note: This will not remove Operating System software from your device (Froyo, Gingerbread, etc.)
Factory reset steps:
1. From the main home screen, select Menu
2. Select Settings, then select Privacy
3. Select Factory Data Reset
4. Select Reset phone
5. Enter the password if prompted, and select Erase Everything
If the device is frozen, follow these steps:
1. Remove and reinsert the battery
2. The device will power on
3. Hold Volume down, Home, and Power buttons until the reset screen appears
4. Select wipe data/factory reset (using volume down) and press Menu
5. Select Yes and press Menu