I solely registered for the purpose of thanking celockwood
and if anybody else should come by this way with the same problem. Just my completed my first gamer PC.
Graphics Card: NVIDIA GeForce GTX 560 SE (was not the problem of-course ^^)
Screen : AOC
Did just like celockwood
said and it work 100% for me. If you should ever read this, THANK YOU A 1000 TIMES!