Poor video playback

Hi everyone. I love iTunes for renting movies but the playback is terrible. Often the video will freeze for several seconds, then when it starts the sound is out of sync forcing me to exit, start the movie again and try to find where I left off. That happens about five times during a movie.

I've read a multitude of threads online but there doesn't seem to be a definitive fix, and solutions seem to vary wildly depending on your system and setup. So I was hoping I might get help here. I'm happy to post whatever info might be needed to work out a fix.

Thank you kindly.

Win XP service pack 3

AMD Athlon 4600+ dual core

4 gigs ram

Creative SB Audigy 2 ZS

1080p display