87xx series, 81xx series, and 88xx series:

1. Go to Options
2. Select Security Options
3. Select General Settings
4. Hit menu key and select Wipe Handheld

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71xx series, 72xx series, 75xx series, and 77xx series:

Option 1
1. Go to Options
2. Select Security Options
3. Select Content Protection
4. Hit menu key and select Wipe Handheld

Option 2
1. Set a password under Options >> Security >> Password and save it
2. Enter that password incorrectly 10 times....
3. After you enter it wrong 10 times it will wipe out all the data