Firstly, this article requires version 6.00 or higher of the advanced or standard codec pack, or a recent and stable version of ffdshow.

Click "Start" and go to "Programs", then "Cole2k Media - Codec Pack" in your start menu, select "ffdshow Audio" and you should see a window open like that shown in the first picture.

In the codecs pane you will see a list of formats, what you need to do now is set the options in the decoder column as follows:

AC3 to "liba52"
DTS to "libdts"
Vorbis to "libavcodec"

The next step is to set ffdshow's mixer to output in the same number of channels, to do this scroll down the left pane of the ffdshow configuration window and select "Mixer", the window should appear as shown in the second picture.

Now in the "Output speakers configuration" drop down box select "Same as input".
A number of other options such as "Custom matrix", "Normalize matrix", "Voice control" and "Expand stereo" should be unchecked.

You should now be able to enjoy AC3, DTS, OGG mutli channel files in full.