More AV geek help needed...

[M Holmes]

I have an Archos AV380. For movies it uses DivX format with CBR MP3
sound.

I've downloaded some episodes of stuff I've missed from tvtorrents.com

These seem to be in DivX format but with VBR MP3 sound (I think).

I use VirtualDub to convert video to the form that can be used on the
Archos. Archos helpfully provide a front end for this with settings as
for the Archos unit. This time it gives a message that there's no audio
codec to decompress the audio. 

As far as I can tell I have Fraunhoffer in there. I tried to install
LAME but it was never clear to me how that was supposed to be done and
it seemed to require too much configuration.

Does anyone have any idea from the above what i need to do? Is there an
easy to install codec somewhere which will do the necessary for
VirtualDub?

Thanks as always...

FoFP