Well it's not a matter of file types. As I mentionned : the MKV files I'm attempting to play on my main PC play fine on my other Media Center PC that is equipped too with PowerDVD 10 Ultra Mark II.
I assume that if one PC manages to do the playback of that files, the other should too ?
And of course hardware wise my main PC is able to handle MKV files (Core i7, GeForce 580, etc).
There you go anyway for the mediainfo report :
General
Format : Matroska
File size : 1.09 GiB
Duration : 43mn 3s
Overall bit rate : 3 632 Kbps
Encoded date : UTC 2010-11-19 02:54:36
Writing application : mkvmerge v3.0.0 ('Hang up your Hang-Ups') built on Apr 19 2010 11:58:49
Writing library : libebml v0.7.7 + libmatroska v0.8.1
Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4.1
Format settings, CABAC : Yes
Format settings, ReFrames : 6 frames
Codec ID : V_MPEG4/ISO/AVC
Duration : 43mn 3s
Bit rate : 3 183 Kbps
Width : 1 280 pixels
Height : 720 pixels
Display aspect ratio : 16:9
Frame rate : 23.976 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.144
Stream size : 958 MiB (86%)
Writing library : x264 core 107 r1745 4785e8e
Encoding settings : cabac=1 / ref=6 / deblock=1:-1:-1 / analyse=0x3:0x113 / me=umh / subme=7 / psy=1 / psy_rd=1.00:0.00 / mixed_ref=1 / me_range=16 / chroma_me=1 / trellis=1 / 8x8dct=1 / cqm=0 / deadzone=21,11 / fast_pskip=0 / chroma_qp_offset=-2 / threads=6 / sliced_threads=0 / nr=0 / decimate=1 / interlaced=0 / constrained_intra=0 / bframes=5 / b_pyramid=2 / b_adapt=1 / b_bias=0 / direct=1 / weightb=1 / open_gop=0 / weightp=2 / keyint=250 / keyint_min=23 / scenecut=40 / intra_refresh=0 / rc_lookahead=40 / rc=2pass / mbtree=1 / bitrate=3183 / ratetol=1.0 / qcomp=0.60 / qpmin=10 / qpmax=51 / qpstep=4 / cplxblur=20.0 / qblur=0.5 / ip_ratio=1.40 / aq=1:1.00
Language : English
Audio
ID : 2
Format : AC-3
Format/Info : Audio Coding 3
Mode extension : CM (complete main)
Codec ID : A_AC3
Duration : 43mn 3s
Bit rate mode : Constant
Bit rate : 448 Kbps
Channel(s) : 6 channels
Channel positions : Front: L C R, Side: L R, LFE
Sampling rate : 48.0 KHz
Bit depth : 16 bits
Stream size : 138 MiB (12%)