Cheers mini,
There is no such thing as a daft question, BUT there is such a thing as a daft answer.
I've noticed that when a cell (mobile) phone is left on in the cockpit, it tends to interfere with the communications systems. I.e. one can hear a crackling noise or noises and that mainly occurs when the phone searches for a new station.
Laptops are no problem whatsoever. We use them in the cockpit (enroute) to prepare loadsheets for the next flight. BUT I don't know too much about CD ROM's in laptops..., what effect they have, that I don't know.
But DO switch off the mobile phone. I think that one can get a jail sentence in Italy for that offence, especially on Airbus aircraft.