Hello, I have got a problem with my acer aspire 5520, at first it worked well but after about 3 months everytimes I play the warcraft 3 game the fan start rambling and the computer bcomes really laggy, the heat is not 2 high, comparing to my friend's laptop, could you guys assist me with this problem? Its really annoying.

Unplug the computer..take the case off (usually a couple phillips screw on the back) check all your fans , make sure they have good compression and dont just spin freely. clean the heatsincs under the fans with some canned air.--dont forget the fan on the video card if you've added a non integrated video card...then check all the ram and cadd-in cards , make sure they're properly seated in thier spots.
You might fire it up with the case off and try to locate the noisy fan or device... most fans can be replaced..any computer store will carry them.
Keep in mind a fan CAN make annoying noises as it starts to go bad..replace it BEFORE it causes other damage, don't put it off if it sounds bad.