Audio, DVDs, and hard drives.?

I recently change from DVD Shrink 3.2 to DVD Fab 6. It all seems to work perfect when I rip the DVD to my hard drive. Then I convert it into an AVI file with WinAVI, but there's one problem. The audio on the final product is always too low. I've tried everything I can think of to fix it, but it all seems to have the same end result, just too low. Any suggestions on how to fix this? Thanks beforehand!