Hi, I recently upgraded the ram in my pc from 1.5gb to 2.5gb as it seemed to be getting pretty slow. I was expecting a pretty big jump in performance but it doesn't seem to have happened. The pc can sometimes be faster than it was and sometimes it really drags. There is also an intermittent loud noise which i believe is coming from the fan and when this happens the pc is slow. I took out the fan and cleaned all the dust from it but this noise still starts every couple of minutes and the pc becomes slow. Any ideas?