Yeh, i have exactly the same problem. I have a Dv6 and whenever i play CoD, Medal of Honor or any other game itjust crashes. I have recently taken it to john lewis as the fan was playing up, so they replaced it. Then my laptop started to shut down when playing games. I can really here the fan working, even in less demanding games. I haven't noticed the game freeze and never had the purple lines. All i have is the 'wheep' sound and shuts down.
I am going to talk to HP and if they have any solutions i will post them to you.