Good to know, that we are not looking at an Win8 issue. I will activate customer support as well then.
I was also investigating fan noise before I got the m4800. And I got it only because of the test results you were mentioning (silent machine without load....).
Please let us know what DELL support is comming up with.
I experience exactly the same on Win7 with a M4800 "called" CA020PM48008MUMWS.
BIOS version is A06. As I saw, A07 is already out, but does not state any improvements in this field, but maybe it worth a try. But a research first to know what might go wrong in A07 is probably a wise thing.
I just wanted to share with you all that for me, I had the exact same issue when I first got my M4800. The fan would go on without substantial load, and would stay audible even if I closed all apps and let it sit still.
I was running BIOS version A03, and I decided to update to BIOS A07. After I did that, the problem went away. The fan does not come on at all, unless the system is really taxed, and I mean, heavily taxed. And when the fans are on, they will turn off when you return to normal load.
Gotta say I'm impressed. This is my first Dell and I really like the computer. It is completely silent for normal office tasks and the keyboard is pretty sweet. As good as my old Thinkpad I would say.
I had the dell pro support to check the device. The A07 Bios had come out the day before they came. So everything they did was to install the bios and the issue is solved. Let's hope there are no more glitches like this for such an expensive device.
I also had the same problem with permanent and noisy fan activity. Now the A07 BIOS has solved the issue and the laptop is at last usable.
A07 solved for me as well (despite it was not stated in the release notes AFAIK), still if a want to be a real fault-finder, I can say that it's a little bit noisy when it starts. But OK, it's far-far better now. (But other manufacturers can produce so much quieter laptops!)
But still, I have to say, there are some traces of the previous buggy behavior remaining, i.e. sometimes I still experience louder noise from the fans, and when I switch power scheme, it lowers considerably. So IMHO it's not totally solved, but now tuned finer.
I have a m4800 as well and I was experiencing the same problem. I upgraded my Bios to A09 and the CPU drivers and it seems to be ok now.