Playing one AVI in WMP there's no audio

[mahogany]

My friend has bought a laptop Qosmio X505, Win 7, 64-bit, CPU i7, 18.3" display. Looks really nice but personally I wouldn't buy such one. Too big and too expensive. Moreover, he has no clue about computers at all. Sounds funny, doesn't it So, in my spare time I show some computer basics for him (I'm not a computer geek either). But let's get to the point.
On his beautiful laptop playing one specific AVI file in WMP there's no audio at all. The same file plays in MPC-HC with no problems (audio and video). I've installed AC3Filter to his system and still no audio playing back same video in WMP. I checked in the list of >associate a file type...< and there was no .ac3 extension at all. Weird...
I checked this AVI by GSpot and can't see any problem. Shows needed codecs installed.
He want to play videos back in WMP... Let it be his way.
I know I don't have to worry about this. That's not my computer. But
1) he is a friend of mine
2) and out of my curiosity

BTW: His other AVIs playback in WMP with no problem. But I can't say for now - was in the other AVIs AC3 audio or some different format - can't remember. I can check it out in a couple hours if this is a crucial thing.

EDIT: The other AVI files with AC3 audio play back in WMP with no problem. Just this file doesn't have any sound. That's what I don't understand

General
Complete name : C:\Users\...........\Documents\So Weit Die Füße Tragen
Format : AVI
Format/Info : Audio Video Interleave
File size : 701 MiB
Duration : 1h 18mn
Overall bit rate : 1 247 Kbps
Writing application : Nandub v1.0rc2
Writing library : Nandub build 1852/release

Video
ID : 0
Format : MPEG-4 Visual
Format settings, BVOP : No
Format settings, QPel : No
Format settings, GMC : No warppoints
Format settings, Matrix : Default (H.263)
Codec ID : XVID
Codec ID/Hint : XviD
Duration : 1h 18mn
Bit rate : 1 013 Kbps
Width : 544 pixels
Height : 304 pixels
Display aspect ratio : 16:9
Frame rate : 25.000 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Compression mode : Lossy
Bits/(Pixel*Frame) : 0.245
Stream size : 570 MiB (81%)

Audio
ID : 1
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Codec ID : 2000
Duration : 1h 18mn
Bit rate mode : Constant
Bit rate : 224 Kbps
Channel(s) : 2 channels
Channel positions : Front: L R
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Compression mode : Lossy
Stream size : 126 MiB (18%)
Alignment : Split accross interleaves
Interleave, duration : 40 ms (1.00 video frame)
Interleave, preload duration : 500 ms