First, try this:
1. From the main home screen, tap menu
2. Select Settings, then Privacy
3. Select Factory data reset
4. Select Reset device
5. Select Erase everything
If your device is frozen and the above doesn't work try this,
1. Press and hold the Power button and then touch the Power off option on the screen to turn off the device.
2. Simultaneously press and hold the volume up button and volume down button.
3. Without releasing the volume buttons, press and hold the power button until the device displays the configuration screen.
4. Press the volume buttons to move the highlight bar on the screen to the Factory Reset option.
5. Touch the Camera button to start the reset process.
6. Wait for the device to reboot.
All of your data stored from the Dell Streak including third-party applications will be deleted . Once the software reset is complete, the phone will then reboot to its factory fresh default state settings