First of all, I doubt it is overclocked if it is an HP, so don't even pursue that Donuts. A little more info is needed though.
Is it locking up after a certain amount of time or immediately after you launch a game?
Are you getting artifacting before lockup?
What drivers are you using?
You should use the nVidia 6.18 reference drivers and if the card is locking up after using it for a bit, your problem is most likely heat related. Try to take the cover off the box for better airflow and see if it still locks. HP cases suck for airflow. If if locks immediately, try uninstalling and reinstalling the drivers. If it still is a problem, try it in a different machine to determine if it is the card. Leadtek has a history of heat problems in their design.
LJ