Memory Loss , Xtron ?

Xtron, TV, Dvd, Mp3, Radio, 12 volt
how can I save the MEMORY on my Xtron RADIO as it
wont save any stations that I put into it.
Sorry no model name the only details ,advertised as,
( Double Din remote control 7" car DVD player with
TV tuner, )
Thanks for any help.

Trevor
December 2009