Make and model.
Get a can of compressed air and every day for a week give the vents a few shots of air.
So I got my girlfriend a high end computer a year ago, all was well till recently. When she try's to play games the fps drops dramatically after a few moments, i.e. we play Conan Exiles, as soon as we load in she can play fine for a minute and then her fps tanks, and in Final Fantasy we que for a dungeon and when she gets in it tanks again. It doesont even out either.

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