With mobo player.
First you tell mobo what directories your movies are located in.
It will index all of the movies it finds there and present a list.
Some times if you get no sound, long press the movie name and select Soft Decode.
I recommend Buzz Player over Mobo. Although both claim to play just about the same types of file formats, I have found Buzz to play better than Mobo. Mobo always gave me problems with certain formats (video/audio syncing issues, amongst other things).
The choice is yours though.
Are both "Buzz" and "Mobo" already on the Thrive or do they need to be downloaded? If they need to be downloaded how is that done? If they are already on the unit, where can they be found?
This is the one I have been using to convert all my videos to HD format to play on my Acer A500. As long as you use the correct output codec, they play perfect. I have had this program for several months. Try the link below for the free factory pro version. It does not have any limits or logos. Not sure the FREE offer still stands, but worth a try.