when my computer starts up it makes a loud noise and when windows stars its kind of slows down. then when im playing a game it gets choppy for no reason. my mouse just skips around the screen. i know its not my video card or ram cause i got a 124mb video card (nvidia) and 1.5gb of ram. the noise started when i installed the ram could this be because i need another power supply? and how do you know if your computer is over heating cause i have noticed that if i put my fan blowing into my computer it runs a little smoother. can someone help?