MPEG-4 VKI codec http://www.divx-digest.com/software/mpeg4codec.html
VirtualDub 1.3c (ima podrsku za ASF support) http://www.digital-digest.net/downloads/files/encode/virtualdub13c.zip
Load your ASF file into VirtualDUB.
From the "Video" menu, select "Direct Stream Copy".
From the "Audio" menu, select "Direct Stream Copy".
Save the AVI file - your have just converted your ASF file to a brand new AVI file - it should have only taken a few seconds for the "conversion", since all you really did was change the container from ASF to AVI.