Comp Problems

[Apac102]

For about 2 weeks now my computer has been running really loud because the fan has kept going. It sounds like when you put a cd in to use or your burning a cd and its working overtime. Its just extremely loud and won't shut up. I went in and cleaned out all of the dust that was in it thinking that the comptuer wasn't getting to cool down properly but after i did that the noise continued right back up. I was curious if anyone knows what the problem is and how i can fix it b/c it sounds like at this rate, my computer's life is dwindling fast.