In reply to andic:
What sort of car is it? Try forcing the window down with your hands, you maybe surprised. Also if its got airbags it may also have auto unlock in event of an accident, so give it a proper good kick on the front bumper, it might "fool" the management subsystem into thinking its been in an accident & unlock the car via the central locking. Also try a metal ruler down the window seal above the lock, you can pull/flick the lock open, but this works best if the ruler has a hook on it.
If all this fails, smash the smallest window, make sure you can reach the door catch though.
Hope this helps