HP/Compaq :: Zd800 Series Black Screen

Whenever I play a videogame (WoW mostly) or run a directx 3d diagnostic the computer freezes up and I get either of two results: one is a "no signal" message from my monitor (lcd screen that I route my screen on, the laptop screen is disabled) or it recovers a few seconds later with a VPU error. it recovers only about 5% of the time, almost always it's the no signal.

I tried installing new drivers, downloading all possible updates, new directx and no luck.
this does not happen every time by the way, and not always when i start the game. sometimes i get no error for hours, sometimes i get one as soon as the game starts.
the only solution that i can come up with at the moment is a hard reset of the system.

I've talked to HP online professional chat service and they told me something completely... useless... for the lack of the better term. something about some games not being compatible with some operating systems...and yeah, i can do everything else.. surf the web, play movies, leave the pc on for hours at a time and no errors, doesn't matter if it's just been started up after 24 hours of rest or if it's hot after 3 hours of a movie, the errors are always there. it's a zd8000 series laptop. ATI Radeon Mobility X600 card, 1 gig ram. about 60% of the hard drive is empty. also I've played the same game for years on it now with no problems.