No audio on an AC3 coding

Hi,
I’m trying to play an old movie (The Lady from Shanghai) from an AVI file. All I get is the video, no audio.
My audio codec is “ac3 (0x2000) Dolby Laboratories, Inc”. When I run Gspot on this file, I get a “Codec misconfigured” report.
I’m running an xp pro (sp2) system.
What should I do to revive my audio?

Ran

Ran,

Try downloading another AC3 codec.