I have Radeon HD 4670 on which I've played games like Crysis I & BF3.
But recently when I played a stupid old Railroad Tycoon 3, PC restarted. This happened twice. I thought some cable or RAM might be lose.
When I checked my GPU, it was damn hot.
So I ran RealTemp GT to check the temperatures.
CPU - 40°C - 48°C
GPU - 68°C - 107°C (idle... ...doing nothing, just FireFox was opened)
I was afraid to test any benchmarks on games.
I noticed then even if I play 480 video on YouTube.. GPU temp escalates quickly.
Right now..I set my cabinet fans to run on 30°C which atleast keeps temp to 68°C, without them it is 80°C.
Please suggest...is related to cabinet or PSU or drivers.
I would check to make sure the fan on your GPU is running. Given the age of a 4670 the fan could have died or you could have a lot of dust build up depending on the last time you have cleaned the dust out of your rig. It really sounds to me that the fan has quit working.