Just tried the new Intel Win8 Beta driver and got the same result as "kaades", a black screen. Furthermore, the High Definition Audio Controller device still has an exclamation mark.
----------
@jlpek: I noticed that the Intel-Inf driver link you provided above is for Intel 7 Series Chipset Boards. How do you know that the Mac Mini Model 2011 has an Intel 7 Series Chipset Board?
I know that the Mac Mini Model 2011 contains an Intel HM65 Chipset and that Chipset belongs to the Intel 6 Series, so I would assume we would need a driver for the Intel 6 Series Chipset Board.
Sorry for the Intel-Inf I think you could find the right one on Intel Download Center.
You can control which "inf" the setup has installed : try the command "Intel-Inf.exe /?". Normally Intel-Inf are needed when a new Intel platform comes after the release of Windows but some update could be made and solve some problem like the one we have here.
What's the problem Windows indicates when you double click on the device ? Is it "the device as not enough memory ..."
For my iMac I have two HDA controller : a CirrusLogic and ATI HDMI Audio which related to my external video/audio output (which is MiniDisplayPort ! I use MiniDipslayPort to HDMI cable and the audio only works by this output when I install the drivers). For this last device I found the driver on Realtek site but it is also on Bootcamp files. Maybe yours is INTEL HDMI Audio or something like that ?
----
I'm wondering about what does the Bootcamp Panel do in BIOS mode when you increase/decrease sound or backlight. Maybe it access to "data/values" that apple store differently or elsewhere (compared to other EFI-computer) and maybe it is some of these "data/values" that our Graphic-Card looking for !