General Tips: Transcoding
From The Neuros Technology Wiki
Try AVIDemux. This easy-to-use open-source program includes a wealth of filters, excellent recovery for damaged or malformed AVIs, and a straightforward interface. Available for Linux and Windows.
ASF to XviD
If you want to convert from the asf format the best non-free tool for the job is Nero Vision Express. Hit make movie, import your asf(s), and then export to whatever you want (XviD for example at 640x480 or whatever aspect and resolution you choose).
To convert asf to avi format without transcoding
You can use a tool called AsfTools. There is a small guide at Doom9.net on how to use AsfTools for this purpose. It is advantageous to convert without transcoding because transcoding results in quality degradation. To transcode a file, the source is decoded and then encoded again; each encoding process gets rid of information. This method converts the asf to DivX ;-) 3.11alpha (note the ;-), sometimes referred to as DivX3, not the same as DivX). It can accomplish this because the DivX ;-) codec is the same as Microsoft's MPEG-4 codec used in the asf file format, but hacked so that it can be placed in an avi container.
DVD shrink is another option for addressing the size problem of putting the information from a dual-layer disk on a single layer consumer disk. Check out the doom9 site for simple tools like this one as well as video editing tools like IFOEdit.