Recently cleaned my machine, put everything back together and all was good, except for the fact that every time the PC boots, one fan in particular at the back of the case sounds like it's taking off. It eventually stops, and the whole thing goes quiet like it used to be. Smacking it when it makes noise helps, but I don't wanna beat my computer senseless. I've tried unscrewing it, and it makes zero noise, making me think it's something to do with the contact on the case itself. Is there some common trick or something I should try? Like a thin cotton or synthetic padding between the fan and the case? Thanks!