I have a 5 year old Pentium 4 that is starting to make noises. The sound is like a motor revving up then slowing down. If I put my hand on any drive, or on the frame, I can feel it revving up then slowing down. (Does this sound like the power supply, or something I can replace?) Other than that, it works fine. I mainly use it for internet, and burning a lot of disks.