I am running it from the CD. However, the CD drive motor only contributes a small amount of noise. I hear the fans "rev" up evertime I boot, regardless of whether there is a cd in the drive or not. I think this has to do with the fact that my PC is a small form factor one, and it probably does that because upon boot, alot of power is drawn into a small space, so the fans are somehow set to go faster because of that. The thing is that the fans die down immediatly when Windows starts running, but not with Knoppix, they just continue blowing really fast.