M8 when i say :Clear the dust, i mean remove the fan totaly,remove(oh my english suxx when it comes to technicals advices
:/\!! )his bearings and totaly dismantel the whole mechanisam...clear all and put some oil ,very little, on shaft.Then it must rotate freely even when u just move him in the air!...Next check the paste between the cooler and the GPU itself and get a new 1 there if the old is in bad condition but first make shure to remove previous layer.Dont put to much!...then go to some benchmark and (if u didnt do something right u will know very fast...system will becom ehighly unstabile and u will have a lot of artifacts even on desktop..) run that program to test your card if it dont freeze or make some glitches and artifacts after 3-4 hrs u r then 100% free from hardvare troubles and u can turn to software issues like bad or coruppted drivers,DirectX troubles,some overclocking residental programs etc,etc...