Vista - Audio limiting mystery.

- The problem
I've got a problem with music files being normalized in Vista.
(Whenever
music tracks exceed a certain level, the volume is reduced
automatically.)
This may happen with all audio streams, but I have only noticed with
music
files.
I've made sure that the graphs are clean (audiofile > codec > sound
renderer), that any players used aren't using limiters and loudness
control
in the Sound Manager for the Realtek HD Audio ALC888 is switched off.

- Things I noticed
The issue seems to be related to (or at least solved by disabling) 32
bit
IEEE float.
Using Graphedit and DScaler as decoder for mp3, setting prefered
connection
type to 32 bit PCM restores audio to normal.
Using Graphedit and ffdshow as decoder for wma, forcing 32 bit PCM
restores
audio to normal also.

Unfortunately, this does not change system-wide performance.
Playback through Windows Media Player still results in the described
problem. I'm guessing this is to do with WMP11 using different codecs
for
playback.
Seems to indicate a fundamental problem (possibly of of the Realtek
ALC888)
with 32 bit IEEE float.

- Attempts at a solution.
* Tried to resolve the issue by looking at ways to set 32 bit PCM as
the system
standard, but the Realtek GUI doesn't seem to provide for it and I
have been
unable to find a helpful Vista setting.
* Failing this I've been trying to tackle this at the codec level.
It's been
just as unsuccesful. Windows Media Player is my main Music Player. I
don't
know which codecs it uses and the Microsoft DMO's aren't directly
configureable.
* To force WMP to play my game I looked at removing all relevant
codecs
except the ones that allow me to set 32 bit PCM as default. However,
in
Device Manager\Sound, video and game controllers I only see "Realtek
High
Definition Audio." No codecs like in XP.

- Questions
Does anyone have a clue what's going on here?

If not
Is there any way to get Vista to force 32 bit PCM system-wide?
How can I manage codecs in Vista (Premium)?
Is there any way to configure WMAudio DMO to use 32 bit PCM?