If its 76 degrees somethings not working right. That cooler looks like a pretty standard tower design, and those should do a lot better than the stock cooler. Are you sure the backplate is installed correctly? You shouldn't have any trouble booting with the screws tightened.
				
			 
	 
 
		 
 
		 . Now my cpu is at 25 degrees celcius in idle
. Now my cpu is at 25 degrees celcius in idle 



 
 
		