i pretend its running through a checkdisk - which can take a while and keep them hanging on, i say stuff like 'ooh yeah it is running dead slow, must be because of what you say, its still running the check and i cant stop it'
they usually wait, though sometimes they say they will call back in a minute
one called me a prostitute once when i came clean what i was doing - wahahahaa!
i laughed my head off down the phone at him.