Need help with my gateway modem password

A long time ago I created a username/password combo for my gateway/router modem (DPC3825).  Guess what I have no idea what they are.  Is there any way I can clear reset the beastie?  I wish to assign a bunch of internal static IP addresses based on MAC addresses but I can't get into the bloody thing.  Any help would be much appreciated!

Ed Brunelle

Phoenix, AZ