Alienware X51 R2 Freezes while gaming.

I've had my x51 for nearly a year now, and I have had this problem of games freezing for the past 5 or 6 months but for other priorities I can only get to sorting it out now. 

Every game i play, it freezes up but sound will continue to play whether its in game sound or music and then I have to do a hard reset. I've tried running diagnostics on it and no problems, updating drivers and everything else i can think of. The only exception is Guild wars 2, some days it runs fine but other days the graphics in game will look as if they are stretching and then 5 seconds later it will freeze. It's even froze up while attempting to find directions on gmaps.

I hope I've not left it too late as my warranty runs out in a month, i just hope to get to the bottom of this as it can be so frustrating. 

Thanks in advance.