When you say fan near hard drive - I assume you mean the Front of case fan?
These are usuall in a plastic 'cage' that latches into the front panel and gentle squeezing of the case near the slots unlatches it.
Then unplug from the PSU harness and lift out.
Then fan it self is screwed or latched into this casing- Now you can clean it and the cage with with damp tissue.
Whilst it is out lift the label on the fan boss and drop in a little machine oil to fill the cup.
Not WD40 that is not a lubricant.
Then reassemble and put it back.
If this is not the fan you are describing go into more detail.
Whilst you are at it- a good clean up of the case,PSU and CPU fans would be useful also.