I have 3 dell 2400's with same processor, celeron, same speed, 2.40. I can put in any dvd-rom player in one machine and it works fine. I'm using vlc player. the one that work only has 1 gig of memory in it. the other has 1.5 gig in them. when the movie is playing, it's jumpy/jittery. I have updated the video driver. any suggestions?