Windows Movie Maker Playback

I am a complete novice so please forgive me. Recently I installed a firewire
card in a 3 year old PC. It's a Dell Dimension with a 2.4Ghz Intel P4 CPU,
512MB RAM and 300GB HD. I captured about an hour's worth of video from my
camcorder (a Sony DCR-TRV120) using the DV-AVI setting. It appeared to
capture successfully, but when I played it back on the PC, the audio and
video contained pauses and hesitations that shouldn't be there. It was sort
of like stuttering - freezing for a split second - choppy. I captured the
same video on a different PC & different firewire cable (Dell laptop less
than 1 yr. old, Centrino 1.66Ghz, 512 RAM, 60GB HD + 120BG Ext. USB 2.0 HD).
It played back perfectly. I figured there was something wrong with the
firewire card (or cable) on the Dimension PC. I connected the external HD
from the laptop to the Dimension desktop and copied the AVI file (the one
that played back fine on the laptop) to the local drive C on the desktop.
After doing this, the audio/video still played back lousy on the desktop PC
(same choppy stuttering). I'm not having any other problems with the desktop
- it's using the same AV software as the laptop. Both PC's are XP Pro SP2.
Any suggestions would be greatly appreciated.
Thanks,
fulx