Does he have the latest drivers installed for his video card/chipset? Does it happen in all browsers? Can you duplicate it with the same website or is it always random? Does it only happen on websites that have flash or video? It might be helpful to have a little more info on the specs of the laptop.
It happens randomly whenever he is surfing the web. It is an Acer Aspire 5750. I just checked for updates, using windows update manager, and it says it's all fully up to date.