There are a few instances in which you may want to perform a reset on your Forerunner 10, such as:
By doing this reset, all user information, workout history, and satellite data will be erased. Workouts can be backed up to training programs like Garmin Connect.
To reset the device:
The reset on the Forerunner 10 is successful if the device finishes powering up and goes to the setup wizard. Try the steps again if the setup wizard does not appear.
Leave the device outside with a clear view of the sky for a minimum of 20 minutes to acquire satellite data.