you can always find the 'factory reset button' and hit that. you may need to open the cam to find it. even if there's no button, there's almost always a couple of pin pads one can short out (with a pin or paperclip) while booting the camera to reset it to factory defaults...
OR follow the instructions found here on the forum to 'update' your cam via TFTPd to the same version it's on now (make sure to use the right version for you cam!). That has the side effect of reverting to factory settings, just like hitting the reset button...