Well you want mplayer installed with gmplayer because gmplayer is mplayer, but with just the added gui.
I installed the MPlayer v1.0pre7try2 source
at the official site and did the following...
Code:
tar jxvf MPlayer-1.0pre7try2.tar.bz2
cd MPlayer-1.0pre7try2
./configure --enable-gui
make
su
make install
You can then use the following commands to activate the mplayer gui...
Code:
mplayer -gui
or
gmplayer
If you're running slackware, there is a tgz package
here.