Newly build pc keep freezing

[chath]

i was recently built a pc. there were no issues at least for a month time(worked on board graphics) but yesterday i installed a new GPU which is ASUS Radeon HD 7870 V2.after that when i playing games pc keep freezing. NO BLACK SCREEN NO BSOD but the last picture known.
ctri alt del is not working. i have to force reboot each and every time.. used furmark in extreme conditions for long period of time but no errors. only when gaming..
pc specs

Intel Core i5 3470 3.2Ghz (3rd Generation)
Gigabyte GA-B75M-D3H mobo
Antec VP450 450W Energy Star Certified psu
Corsair 8GB (2x4GB) Vengeance 1600 Mhz CL9 DDR3 kit
Toshiba 500GB 7200RPM
second pcie poer cable for GPU is molex to pcie converter

please help me with this

 

[chath]

but i used a version of a memtest which work ram and cpu in peak after exceeding 7.840 G ram mem pc crashed it happend several times

 

[smorizio]

first off check the mb bios rev. the newest rev is f14 that i found. the bios rev will be on the first page of the bios screen. make sure your mb has all of the bios patches. with the ram make sure xmp profile is turned on and run cpu-z check that the ram in windows is running at it rated speed and voltage(the spd tab will show you your ram rated speeds). make sure you have the newest intel chipset driver install. the last issue could be that the low end power supply can output the voltage needed for the gpu. one issue if it not power then it could be that the gpu fan not ramping up to keep up with the heat. try running msi afterburner make a fan profile. and check that the gpu fan will spin up to it max speed. if you have a mini or small case if you think it heat issue take the side panel off. I would also run hardware monitor to check your cpu and gpu temps..post them up here to see if there getting to hot.

 

[chath]

i think issue is power i monitored all hardware temps they are in normal range ran intel burn test in extreme condition turns out ram and cpu is stable under normal voltages.
i removed one ram stick and disconnected ASUS rom now system is stable. new psu will solve my problem yes?

 

[chath]

Best answer selected by chath.