MyMedia only supports what the Roku supports - mp3, wma, mp4, mov. Any other video formats require transcoding. There's a couple of other channels out there that have some sort of transcoding, but I haven't tried any. I find it's much easier (and to me, makes more sense) to just re-encode to a compatible format.
For the registration thing, I'm not sure why sometimes it doesn't work. The workaround that seems to work is to edit config.ini in the server directory and just add the registration code manually:
regid = abcd
Replace 'abcd' with the four character code shown on your screen and restart the server.
If you aren't seeing your videos or photos, make sure the paths are set correctly in config.ini. It's just a simple text file.
Good luck!
-JT
Roku Community Streaming Expert
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