Computer Help!!

Make sure the fan plug is properly seated on your motherboard. You can check your bios settings to make sure the motherboard fan controller is on or at full speed. You can gently move the fan blades to see if it moves and also feel if it is seized up or obstructed.

If that doesn't work you can move the fan plug to a different place on the motherboard or if the fan came with a molex connector adapter try using that.

Also, luckily for you the cooler you have is capable of light passive cooling, so you should be able to safely have the computer on and running to do light stuff until you figure out the problem or replace the fan. Just don't get greedy and spend more than 30 mins at a time unless your temps really are low. Cooler master may also replace or RMA the fan for free depending on when you bought the cooler, should you find it to be dead.

Check if the pin connector of the fan is correctly plugged-in on the MOBO.

Do you have a Beeper connected on your motherboard? If yes, does it "bip" in a strange way (like something u never heard)

When you were cleaning your pc the computer was in power? cause that be both dangerous and bad for the computer my first guess would be the cord that connects the motherboard and the fan its unplugged even partly so power doesnt go through

You should test another fan where the CPU fan is connected to discard any motherboard failure. If the heatsink fan is faulty you can replace it with any 120 mm fan.

Cleaning computer is equal low noise. My i7 920 is a reactor when work's,,,,in windows is quiet mode....silence...silence...ssshhh ;)

If the fan was already making noise prior, from experience I'm betting you inadvertently blew dust into the bearings while cleaning and it got stopped up completely. You can try disassembling the fan to really get all the dust out, or just buy a new one.