You can overclock the movieplayer if you download the new version of the movieplayer (http://www.gp32x.de/board/index.php?showtopic=30454) and then create a launcher script like this:
#!/bin/sh
/mnt/sd/cpu_speed.gpe 1 2 270 1.0
cd /mnt/sd/mp2x/
./mp2x.gpe
sync
cd /usr/gp2x/
exec...