use compressed air and blow the dust out of the case.
And do it Outside! :lolg:
What I do is: Power off the PC then remove the power cord
-Hold the power button in for about 10 seconds to discharge the caps
-Plug the power cord back in then touch the metal chassis of the case
and R&R the memory, touching only the cardboard edge and not the modules or the gold contacts.
-Make sure the notches in the memory are lined up correctly and be sure you hear the locking tabs click on each end.