Why is my computer loud?

my hard drive spins very fast for no apparent reason, im very good with computers and have a 2 year cirtificate for working with computers through boces, but i dont understand at start up its normal i bring up task manager and close everything that is not needed to run, i then run internet explorer or a game and the hard drive goes crazy, sounds like its slowing down then getting fast and slowing down, also i use system mechanic and i did a defrag, and it shows the sectors and the whole outer ring is black? i checkd for bad sectros and nothing, im soon upgradeing to 4 GB ram and thinking about upgradeing to a 500W power supply and a 200 GB hard drive, i clean my computer every sunday with adware system mechanic and reg booster, my computer is always in shape but im just very confused, it gets so loud i can turn my surround sound on full blast and still hear the computer . : /

Why is my computer loud?computer virus

if it's loud then it's cool, check the speakers and buy new ones cause i don't think you wanna spend money on this just try to get used to it or turn the sound off.

Why is my computer loud?free spyware remover

it maybe the fan, or even the type of computer u have.. if u hav something with a fast processor, then it is most likely the hardware like the fan.. hope it helps
Maybe it's the fan.
Its the fan and try to make sure your computer is not constantly on for hours because this will cause overheating thus causing the fan to run at higher speeds resulting in loud rotational sounds.