As far as any data that is stored on the SD Card(images, music, etc.), it will not be erased. Only the phones internal memory is formatted.
If that doesnt work, try is this way:
1. With the device powered off, hold down the volume up rocker while pressing the power button. Next, release the power button on the Galaxy Tab splash screen. The download icon will be flashing, press the volume rocker up to select the Android+Box icon and the press the volume rocker down to select.
2. Using the volume rocker key, highlight wipe data/factory reset and press the power button.
3. Using the volume rocker key, highlight Yes- delete all user data and press the power key.
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