As I mentioned in my first comment within the immediately preceding thread, I bought the DSM 750 for the sole purpose of playing/streaming videos formatted in Matroska/MKV files from my Windows XP computer to my 1080i/p Pioneer Plasma HDTV.
Prior to making my purchase, I was assured by no less than 3 different Dlink techs, including ECF here, that the 750 was designed to do just that, since my previous DSM 520 didn't have a fast enough processing chip for this purpose.
So far here's what I have discovered about my new DSM 750 as to this issue and others set forth below:
1. First, the "good news." You can use the USB port to play MKV files with no problem. Of course, this means that (a) you will first have to copy each file onto a USB flash drive; and (b) the flash drive will have to be big enough to hold these files. By the time this is done, I could have just as easily hooked my laptop directly to the HDTV and played these files through the VLC player. In any event, I didn't purchase the DSM 750 for this purpose; I bought it strictly to stream these files to my HDTV.
2. Now the "bad news." Streaming MKV files from an XP computer appears more difficult, if not impossible, because (a) Dlink's original Media Server software, even with the most recent update, refuses to recognize these files (which probably explains why Dlink no longer provides this software on its installation CD shipped with the DSM 750); (b) Windows Media Player 11, recommended by Dlink in its Manual, doesn't resolve this issue, nor apparently does Windows Media Center Extender software as indicated by Dlink's own ECF in an earlier thread here; (c) Divx PC Connect media server, recommended by Dlink on this website still doesn't solve this problem for the 750 (though Divx claims that MKV files will stream to the DSM 330, which plays at 720i resolution); and (d) Dlink's R&D Dept. just isn't smart enough to figure out how to solve this problem; otherwise they would have done it already since the first 750 shipped almost a year ago.
3. There is a "work-around" to the streaming issue. If you have the time (which I don't), MKV files can be re-encoded/transcoded to AVI files suitable for successful streaming, although I am sure the resolution/picture quality suffers in the process.
4. Additional negative issues/changes with regard to the DSM 750, as compared to the DSM 520 include: (a) you can no longer make volume adjustments with the remote control; and (b) you can no longer "jump" instead of fast forwarding. Personally, I miss both these "convenience" features, especially the "jump" one, since the fast forward feature on the DSM 750, at its fastest speed, moves at a snail's pace.
In light of the above, I'm not convinced that replacing a 520 with the 750 is worth the trouble or added expense, given its limitations and deficiencies. I would also like to hear an explanation from Dlink as to why, if the DSM330 can play MKV files with the newest Divx PC Connect server software (albeit at a lower 720i resolution), this still remains an unsolved issue in the DSM 750, as clearly indicated by several threads here, as well as ECF's responses thereto.