I'm running the latest Mac Pro, bought this past month. It is the default model with the ATI 2600 video card. I was doing some reading a while back on how some people were having issues with the 3870 fan being loud and they had said prior to installing the card, their computer was virtually silent. I'm a little confused by this because my Mac Pro is not loud by any means but it is definitely not silent. I don't remember hearing the demo models in the apple store running at all but with my computer in my room, I hear a constant woosh/hum that I always assumed was one of the fans. What confuses me now is I took of the side panel tonight and it seems like the noise is coming more from the Mac hard drive. I even stopped the front case fan just below the hard drive and did the same with the video card fan and neither of these were the ones causing the noise. The sound I hear is not hard drive writing noises or anything like that, it's always constant, which is why I though it was a fan but I don't see any other fans unless there are more directly above the hard drives where I can't look into. If I use my ear as a guide, I'm continually brought back to the front of the case right near the mac hard drive. What confuses me further is I have 2 other drives installed but the noise is definitely centered around the first drive only. How would you all describe the noise level of your Mac Pro? If the room was completely quiet, would you hear your machine at all or is it totally silent??