<p>
openlp.org doesn't currently support DVD's.
</p>
<p>
We use VLC at our Church, it's open source and can be configured to control on the primary monitor and play videos on the second monitor. without having to do split second dragging of windows! (You can even configure it to play on two monitors at once, although needs good hardware and a bit of playing around in the options!)
</p>
<p>
Alternatively you could try converting the DVD to video files.
</p>
<p>
Regarding the AVI problem. Does the video appear on the preview or the main screen, or does it not appear at all? Can you try going into the Options -> Settings menu. On the Display Settings tab, click the "Use Video Mode Rendering" and see if that makes a difference. (Assuming the AVI plays in media player/other software OK)
</p>