with an avi2mpeg(free) program you can convert any avi that yer comp has filters for to an mpeg(1 or 2) format, also the panasonic mpeg encoder can do this (commercially available but isnt too pricey)
then you can convert to avi or other formats (mpeg to divX or subformats or mpeg2asf)
just search around for these tools you'll find them
you should know that converting will always incurr with a quality loss and 2 conversions may have a heavy (visible) quality loss also make sure to make the conversions at an as high as possible quality and be prepared to take at least some days time for it (even an athlon XP 1800+ cant do 30 fps encoding at High quality so be prepared to sit and wait for a while
Hope I helped you out a bit but I need more info of what TO you want to convert the divXes (if it is RM format there is a more efficient ay for instance ..)