Im not too sure what skin ur using, would be useful im using cdrskull's FU skin, and Got DVD working fine using powerdvd.
Change or Add the below line in place of ur (LOAD;PowerDVD_player.skin) in FU's case, its menu.txt.
&mainbut3=DVD@icons\dvd.png@LOAD;powerdvd_player.s kin;C:\Program Files\CyberLink\PowerDVD\powerDVD.exe;DVD&
i guess u just need to add the location
NOTE: &mainbut3 is the button location
that should get u goin