how do I get a Quicktime video window to play on an external monitor, simultaneously using the laptop for something else? Using Macbook using OS-X 10.5.8, how do I get a Quicktime video window to play on an external monitor, simultaneously using the laptop for something else?

I have a Macbook circa 2008 which has OS-x 10.5.8.  I recently installed an HDTV in order to watch videos from the Macbook on a larger screen, while continuing to use the laptop for other things. I am unable to play a video on the larger screen unless in the mirror arrangement of the screens.  With a side-by-side arrangement,  I can drag the folder which contains the movie, but when I click on open, it opens and plays on the Macbook instead of on the tv.  Other folders also open in the laptop window, not the tv.

http://uk.answers.yahoo.com/question/index?qid=20080914024038AA5ivCZ

This suggestion of dragging the window doesn't work.
In Quicktime Player, go to Preferences. Under "Full Screen", there is a picture of your screens similar to the Displays pane of System Preferences. If you click on a screen, a picture of the QT Player logo will be overlaid on that screen. The screen that has the logo is the active screen for Full Screen Mode.

EDIT: I don't know if you can still do other things while QT Player is full screen.