After two nights of trial and error, i finally set up my online KaraOK system to play one dual monitor - one monitor shows the video playing and the other monitor shows the playlist.
PS. The KaraOK system I use is from
www.51mike.com. It cost less than $20 to become a life time member!
To enable the dual monitor mode, you first need your video card support. In my case, i have an ati card, so you need to enable its theater mode - download its control center and under video category, enable theater mode.
also, you need to enable your windows media player's overlay mode, since 51mike software uses that internally. In my case, i am using windows media player 10. Go to tools -> option, performance , advanced , video acceleration and check use overlay.