po51uhd 0 Newbie Poster

I have an HP Pavilion dv1000 series laptop. I used to be able to display a 'clone' on either an external monitor or projector, but it's stopped working.
When I hook up the monitor and toggle fn-F4, I still get the laptop behaving as if there's an external monitor attached, but nothing happens on the external monitor. Also, the monitor think's it's attached to the laptop because it loses the self-test display, but I'm left with a blank (black) screen on the external display.
I've tried HP help and they're still thinking about the problem after getting me to uninstall the Intel 82852/82855 GM/GME Graphics Controller without success.
Any bright ideas?