[CoffeeShark]

get some canned air first, blow out everything you can.

you can leave off the side of the case, but airflow should actually make it cooler with the side on - directs the air from front to back, instead of it going out the side. This is only if you have good ventilation front-back (no clogged filters).

get the filter cleaned off - canned air, vacuum, whatever you can do, it needs to be clear. if you can't clean it, rip it off - you're better off with dusty airflow than limited airflow.

and please clean your computer monthly, people.