Windows – No DTS Audio output in Windows 7

Windows 7 supports a ton of video codecs by default, but I've found that some of the videos I have will play video but no audio.

Using the MediaInfo application, It looks like the culprit is the DTS-only audio on these video files:

General
Complete name        : C:\Users\Jeff\Videos\video1.mkv
Format               : Matroska
File size            : 7.95 GiB
Duration             : 2h 13mn
Overall bit rate     : 8 517 Kbps
Encoded date         : UTC 2010-10-09 19:46:55
Writing application  : mkvmerge v2.9.8 ('C'est le bon') built on Aug 13 2009 12:49:06
Writing library      : libebml v0.7.7 + libmatroska v0.8.1

Audio
ID                   : 2
Format               : DTS
Format/Info          : Digital Theater Systems
Codec ID             : A_DTS
Duration             : 2h 13mn
Bit rate mode        : Constant
Bit rate             : 1 510 Kbps
Channel(s)           : 6 channels
Channel positions    : Front: L C R, Side: L R, LFE
Sampling rate        : 48.0 KHz
Bit depth            : 24 bits
Stream size          : 1.41 GiB (18%)
Title                : English DTS
Language             : English

(I removed the video section as it isn't relevant)

There is no other audio stream in this file — only the DTS. Clearly it is the culprit for my "video but no audio" problem. So I have two questions:

1. Why can't Windows 7 play back DTS audio out of the box?
2. How do you add DTS audio support to Windows 7 without installing a whole bunch of crazy new codecs I don't want or need?