PC Freezing, i need help

[montana101]

computer specs: Intel Core i3 3220 Standard Intel CPU Cooler, OCZ ZS Series Power supply - 550 Watt, 8GB RAM, 1TB HDD.

Problem is my friend sent my Nvidia GTX 460 which he had from 2011 while i was currently using integrated graphics (Intel HD 2500), when i received the card from him, i installed it, plugged 2x 8pin psu connector etc, when i got it running, later on the day my pc started freezing completely while e.g. browsing internet, playing games, and i had to restart my pc (restart button on my case) in order to get it working again , even when i restarted the pc, it would freeze again in like 1-2 hours and its very frustrating because im worried it might damage my computer.

i decided to take out the GPU for now, i connected my monitor to my normal motherboard integrated graphics and now my pc works fine without any issues/freezes what so ever, so i want to ask whats the issue here?

1) Could it be my CPU cooler ?
2) PSU ?
3) could GPU be faulty ?

Please if anyone has a solution let me know asap below, i cant play games with this integrated graphics as i lag really badly and was looking forward using the Msi GTX 460.

 

[amalts01]

the minimum required PSU is 450 Watt and you have 550 Watt so it's not gonna be the PSU problem
just open the cpu case and clean the fan maybe it would be overheating a nice cleaning can do wonders to your PC and check the GPU on other computer and make sure it's not faulty