BACKGROUND
Highly dynamic music files (tracks with a wide range of high/low loud/soft
sound) seem to get limited.
Entire "overall loud" segments are reduced in volume, as are segments with
"range peaks" (hard bass, hard trebble, but the rest is normal).
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.

Problem 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, setting output to 32 bit PCM
restores audio to normal also.

Unfortunately, this does not change system-wide performance.
Playback through Windows Media Player which forces the use of Microsoft WMA
DMO, for example, still results in the described problem.
Seems to indicate a fundamental problem of the ALC888 with 32 bit IEEE float.

QUESTIONS
Is there any way to get Vista to force 32 bit PCM system-wide?
Is there any way to configure WMAudio DMO to use 32 bit PCM?
Failing that, how can I manage codecs*?

In Device Manager\Sound, video and game controllers I only see "Realtek High
Definition Audio." No codecs like in XP.