I didn't know if you were using the laptop as the Plex server or for playback. You said you watched mkvs "on your dedicated HT room" so I thought you had a HTPC.You need to have the Plex server running to access any media from it. Probably the cheapest route would be to re-purpose a desktop PC to use as a media server. If you don't have one you might find a friend or relative that has an old one that you can have for free.
3/9/14 at 9:43am