So, in the meanwhile I've spent some time looking for an answer and/or a solution, and even if I've found several thread talking about System Insight Manager, Control Agents, and so on, I still haven't understood if it's possible or not to actually control the speed of the fans to reach an acceptable volume (something like 1000/1500 rpm against, let's say, the current 2000/2500rpm, at least considering the sound)...anyway, what comes out is that are needed specific softwares and services to make the System Management working, but looking at the DL580 G5 Downloads Page there are so many downloads that have made me confused! And what is more frustrating is that I've already and installed the most of them, but I still can't see any Item in the System Management homepage, I'm not even able to read the actual speed of the fans. So now I have a lot of stuff installed that I'll probably never need (consider that I'll use this machine only for Rendering/Dynamic Simulations), and I can't find out.
I was thinking to make a clean install of windows server 2008r2, install the driver and only the software I need to manage fan, temperatures and hardware maintenance in general, but I'd need some indication about which of the software in the webpage linked above is necessary to have a full working System Management Interface (with fan speed adjustment if possible), and nothing else.