How to reset a NUVI for a handme-down?

on factory reset.

You can delete an unlock code the same way you created it.

This is from the Garmin.com website:

Question: How do I perform a master reset on my nuvi 200, 205, 465, 500, 600, 700, 705 or 1000 series device?
Answer:

To perform a Master Reset on the nuvi 200, 205, 465, 500, 600, 700, 705, 1200,1300,1400 or 1600 series device:

Note: A master reset will erase all waypoints or favorites and will restore your unit to the default factory settings. If you would like to back up your favorites you can find instructions to do so here.

1. Start with the unit OFF and unplugged from power
2. Touch and hold the lower right corner of the screen with an index finger or the eraser end of a pencil
3. Continue touching and holding the lower right hand corner of the screen then power the unit ON
4. Release the power button when the device powers ON
* You will see a new message: Do you really want to erase all user data?
5. Remove your finger from the touchscreen when this message displays
6. Touch Yes

The device will automatically reset. Follow the on screen prompts then place your device in an area with a clear view of the sky until it acquires satellites.

To copy favorites to another unit.Connect gps to computer.Go to your Garmin folder then the GPX folder and find current.gpx.Copy it to computer and rename it to temp.gpx.Paste copy in the gpx folder on other unit.

You can also use Mapsource.Hook unit up to computer.Click on transfer then receive from device.You will now see favorites on screen.Unhook unit and connect new one.Select transfer again and then select send to device.Reboot and they should be there.