1990 Honda Accord door won't open or unlock

My girlfriend recently bought a used 1990 Accord and now the driver's side
door won't open. It has power locks, but no matter how you unlock/lock it
(power, with key, manually) the locking mechanism doesn't seem to disengage
on the driver's side door even though the button moves up and down on the
door panel. Neither handle (inside or outside) seems to make any
difference, but both have some resistance, which tells me the linkage is
all still intact. It sounds like it is a faulty locking/latching
mechanism, which I think can be replaced, but how in the world can I get
the door open now? Is there a way to disengage the lock or something from
the inside so I can open the door? To make matters worse, her father is a
Ford man and was opposed to buying a used Honda but I argued how good
their quality was and all that stuff and she bought it against his will
and now this happens.

Anyway, any help at all would be greatly appreciated.

thanks in advance,

Fred.