PC freezes/crashes with weird colours after 5 minutes of gaming

Hi, I just got my brand new gaming PC delivered and after I installed all the essentials i tried running Heroes of Newerth and 5 minutes into the game my PC crashed badl. The game screen froze and it got all blurry and colorful and there was a looping sound coming from the headphones. This problem persisted all day on few more games, the time before the crush varies though. I just played 2hrs of Swtor and it was fine until it suprised me with another crash.

I did alot of browsing here and there and tried many things. I tried uninstalling one of either the Realtek or the Nvidia sound drivers, because someone suggested that the sound drivers might be in conflict. I tried puting the RAM in the spare slots, I also tried reinstalling graphics drivers and motherboard drivers. I have also checked all the fans and they are working perfectly fine at all times.

I am using a 64bit Windows 7
CPU - Intel Core i5 2500k
MB- Asus p8z68-v LX
RAM - 8gb Corsair 1600mhz Vengeance (2x4)
Hard Drive -1tb S-ataIII 6.0gb/s
Graphics - Nvidia GeForce GTX550 Ti1GB
PSU - 600W Xigmatek

I would appreciate any advice on how to approach this. The PC is ONE DAY old and its really frustrating to have this problem since I have been saving up for a new PC for few months now....