ok first thing first what temps is your laptop getting it could be just a simple temperature issue you can use a program called HW monitor ( i would run heaven benchmark as well to get the max temps on a fully stressed gpu) to check if you don't understand it then just post a screenshot of what that says now since this is a laptop if i were you i would clean it out with compressed air from almost any tech store make sure you keep it upright (or it sprays liquid) and use it in a well-ventilated area and just spray out all the dust that could be blocking air flow.
now after that, i would go and check to see if its still the issue is still there if not then all done
now if it still is it will help if i know more about what im working with
what model of Alienware laptop? and it will also help me to know if you are still under warranty as you might have to send it in if we can't figure this out.