Are you on a notebook? If so, try plugging the power cord. Otherwise try to check if Powersave is set on Balanced or Maximum Save. In that case most times cpu works only on few cores and external graphics is excluded
Guy, if you're gonna ask for help remember that we're not beside you in front of your screen. So, please, help us helping you by giving us some details such as log.txt, hardware details...
And remember, this is a forum. It is different from Twitter. Here you can, no, you MUST use more than 150 digits to explain your thoughts