I'm, guessing you mean a factory reset, which will wipe the data and leave it in factory new condition. If so:
Turn the unit off. Press and hold both the power button and the volume button at the same time, until the little yellow-green android robot comes on the screen. You can then release the buttons. You will eventually get a menu (this took a while to come up). Use the Volume button to scroll down to "Reset to Factory Standards", and select by pressing the power button. You'll get a msg. that asks if you're sure you want to do this. Use Power button again to select "yes". It will set the unit back to what it was when brand new.