Problem to join 2 avi's with different audio stream format

[nymeny]

Hi guys,
I have a problem with a 3 CD's movie that I want to join them into a single file.
All three parts have VBR audio format.The second and the third part have the same 48000 khz 164 kb/s tot, Joint Stereo Lame 3.92 format, but the first have 48000 khz 155 kb/s tot Joint Stereo Lame 3.92 format(according to Gspot).
Now, I have joined without any problem the last two parts with VDub-MP3, but I get an error message when I tried to join the first and the new joined file, cause of the different audio format.
I supose that I have to change one of those formats to the other, but I don't know how without audio/video desync (tried with VDub-MP3).
Also I want to keep the video quality....
I would appreciate very much any help.
Thanks.

[Inuya5ha]

VBR MP3 is a format specially designed to make its edition impossible by all means.

You'll have to convert those to CBR before anything. Read here for the procedure using VirtualDubMod.

[paglamon]

Try AVIMuxGUI.

[nymeny]

Thank you very much Inuya5ha and Paglamon for your advices.I've solved the problem using VirtualDubMod for convertion and VirtualDub for re-muxing. In a strange way my VirtualDubMod version (1.6.0.0. Sorround) couldn't make a sync movie, but I have handel it with VirtualDub. Many thanks again....