Add new menu entry to all files

This will add new menu entry.
This example will let you try to play all files with MPlayer media player:

reg add "HKCU\Software\Classes\*\shell\Play with MPlayer\command" /ve /t REG_SZ /d "\"%~dp0mplayer.exe\" -fs \"%%1\"" /f

You need to place this batch file in the same location where mplayer.exe is having a good time. Run it with current user rights.