Desktop frezes while playing some games

[IamAnAnt]

hey guyz

I have a desktop with the folloing components:
- dual intel Xeon E5430;
-8gb DDR2 RAM;
-NVIDIA GeForce GTX 750Ti;
-Motherboard Dell 0RW203.

The problem doesn't happen with all games, I've been playing The Witcher 2 and Darksiders with the grafics at medium, but when I play games like LoL the computer just freezes and doesn't responde to any comands (Ctrl+Alt+Del, the keyboard does not activate the Capslock ligth. . .). I think this migth be a Ram problem but im not 100% shure about it, could you guyz give me your opinion?

 

[IamAnAnt]

UPDATE:
i've ran some programs to bench the computer, and it doesnt seam to be either RAM or heat problems

 

[jaslion]

hey guyz

I have a desktop with the folloing components:
- dual intel Xeon E5430;
-8gb DDR2 RAM;
-NVIDIA GeForce GTX 750Ti;
-Motherboard Dell 0RW203.

The problem doesn't happen with all games, I've been playing The Witcher 2 and Darksiders with the grafics at medium, but when I play games like LoL the computer just freezes and doesn't responde to any comands (Ctrl+Alt+Del, the keyboard does not activate the Capslock ligth. . .). I think this migth be a Ram problem but im not 100% shure about it, could you guyz give me your opinion?

Whats your psu?