Usually on a HP, there is a tiny LED light next to the camera that is built-in to the lid, this tells you if it's on or not. On the other hand you need to download HP Camera software that is compatible with your laptop. I recommend downloading this:
http://hp-mediasmart-webcam.software.informer.com/download/?cf82 32Bit
http://hp-mediasmart-webcam.software.informer.com/download/ 64bit
You can find out if your computer is 32 or 64bit by right clicking on "Computer" in the start menu, and then clicking properties.