AVI and MPEG playback stuttering

Recently I've had a problem with .avi's and .mpg's are
stuttering or the video is pausing for a second or so
while the audio continues and then it catches up. I'm
playing these from my hard drive. I did recently changed
my CD-RW to a new DVD-RW but I'm still using the same
burning program (Nero). I've replaced my video drivers
and codec just to be sure they weren't corrupted.

The system is an AMD2800+ with 1gb of Mushkin Dual
Channel 400 Mhz RAM and an ATI 9500 Pro.

Any thoughts and aid would be appreciated.

Boom