GPU is heating up!

so, here comes my story: i have played MW2 for a long time, then when i started it again, there was issue, i play around 5-30 min (seems to be random) and then black screen pops out and i hear endless sound from my speakers. there reads on the screen: ''monitor going to sleep''. same thing as u let ur computer be idle for a moment then the monitor sleeps that it saves energy blah blah... anyways then i downloaded program named speedfan, cuz one guy on the internet said it can be that ur fans are not circling around fast as it should be. hmm, i cant/ i dunno how to change that, but then i found one thing from the speed fan:

GPU temp: 75C
i was like wtf? sry for bad lang but really 75C it is quite lot... so if sumbody could help me i would really appreciate that. please help me!