It's probably just dusty. They get dust on the blades and get out of balance and make a grinding noise. Blow onto it hard - assuming it's the case fan and not the CPU fan (which is probably harder to get at).
@hippy started
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It's probably just dusty. They get dust on the blades and get out of balance and make a grinding noise. Blow onto it hard - assuming it's the case fan and not the CPU fan (which is probably harder to get at).