Some of the Movies have sound after encodeing and some don"t because the Audio in the Source AVI file was of an Unsupported format...If the audio in the Source AVI file is either AC3* or VBR MP3 then Tmpgenc can not decode it, so with those Types of AVI files you have to extract the audio from the AVI file to Wav format then use the Wav file as the audio Source in Tmpgenc...You can extract the audio useing Virtual Dub but if the audio in the AVI file is AC3 audio you can install a Filter that will allow Tmpgenc to decode the audio ..(
http://fcchandler.home.comcast.net/AC3ACM/AC3ACM.zip)
If you have an AVi file that you encode but it the Mpeg file is Just the first Frame of the AVI file for the whole Movie then this Problem can hopefully be fixed by going to "Options" to "enviromental settings" to "Vfapi plugins" and Raise the "direct show" to "2"...If that doesn"t work then there might be an error in your AVI file which you might be able to fix useing something "DivX Anti-Freeze" or "DivX Fix".....good Luck