Nexus One - How to Hard-reset the Nexus One

1. With the phone off, hold the Volume Down button and press and release the Power button.
2. You'll boot into the menu you see above with the famous android robot. Select Clear Storage from the list by pressing the Volume Down button.
3. Press the Power button, and confirm by pressing Volume Up.
4. Sit back while your phone reboots in its virgin state.