Sorry, TMPIN2 is a 'dead' sensor. It's on the chip, but not connected to anything, hence the 128 degree is just strange readouts. This is the fault of the program to display such high temp. To get stable temp better use Everest or CoreTemp above.
About your problem, maybe it's your VGA card or motherboard's VGA slot that is defective. Try replace your VGA with your friend's working VGA. If his VGA works, then you got a defective VGA. If his VGA still doesn't work while his VGA works normally in his computer, then the motherboard's VGA slot is defective.