Well, it might be possible... You could try with xine, it has been reported to give the best performance on older boxes.
Try disabling as much unneeded services as possible in vasm :
VASM -> SUPER (give root password) -> SERVICE -> SRVSET -> (choose the runlevel you use. by default vl boots to runlevel 4).
If performance is not as good as you'd like, you can use a little trick with the "realtime" kernel module. Please note I have not tried this myself, as I don't have a dvd player for my old laptop (it's a 333 MHz p2). I use the realtime module for audio production on a more modern computer though.
1) change the group of the xine executable to "video":
chgrp video /usr/bin/xine
2) load the realtime module and give programs belonging to the "video" group (group 18) realtime priority
modprobe realtime gid=18
3) if it's better, you can add that line to the end of /etc/rc.d/rc.local