Computer Starts Sometimes with Loud Noise

[krupp steel]

Occasionally, I start my computer and a really loud, fast, noise comes from my computer (I think it's the fan), and it would stay like that unless I restart my computer, or turn it to sleep mode and then the loud noise goes away.  Does anyone know why and what will it do to my computer in the future?

[Cranialwizard]

Occasionally, I start my computer and a really loud, fast, noise comes from my computer (I think it's the fan), and it would stay like that unless I restart my computer, or turn it to sleep mode and then the loud noise goes away.  Does anyone know why and what will it do to my computer in the future?

Try cleaning your fan?

Is the computer an HP?
My HP notebook had fan problems from week 2. They have inexplicably loud fans and they often fail for some reason. Engineering at the finest.

[Walentin 'Walki' L.]

Occasionally, I start my computer and a really loud, fast, noise comes from my computer (I think it's the fan), and it would stay like that unless I restart my computer, or turn it to sleep mode and then the loud noise goes away.  Does anyone know why and what will it do to my computer in the future?

Fan speed usually increases with increasing temperature. Are you sure the fan is mounted correctly?
Another solution (like Cranial suggested): Open your computer case and go through everything with your vacuum cleaner (be careful that you don't bend/break anything and detach all cables ofc). If you clean a fan hold it with one finger (don't let it rotate with the vacuum cleaner it might look funny but it is bad for the engine). Make sure to clean the radiator block too, you can do that by placing the vacuum cleaner at the side of the block. Same goes here as above! Don't break/bend anything! Make all this at your own risk.