Hrm, you lost me there...
If you don't have MPlayer OSX, get it here:
http://www1.mplayerhq.hu/MPlayer/releases/MPlayer-dev-CVS-050904.dmg
When the disk image file finishes downloading, double-click on it. You should get a window showing MPlayer OSX and some text files. Drag MPlayer OSX to your hard drive's Applications folder.
Then Open your applications folder and click only once on MPlayer OSX (the program) to select it. From the Finder's File menu on the menu bar at the top of the screen, choose Get Info. Check the checkbox named "Open using Rosetta" and then close that window.
Now to run it...
1] Double-click MPlayer OSX
2] If the playlist window is not already showing then pull down the Window menu on the menu bar at the top of the screen, select "show/hide playlist"
3] Find the mpeg file in Finder (on your Desktop or in a folder) and drag its icon into the MPlayer OSX playlist window.
4] Select the file in the playlist window so that the line with the file's name is highlighted.
5] Click the "i" button for info
6] If the Movie Info window opened, tell us what is in the File, Video and Audio format fields.