WMV is a generic name of Microsoft's video encoding solutions and doesn't necessarily define the technology what it uses -- since version 7 (WMV7) Microsoft has used its own flavour of MPEG-4 video encoding technology (not very surprising, it's not compatible with other MPEG-4 technologies..). DivX ;-) video format is originally based on hacked WMV codec.
The latest versions of WMV (now, summer 2005, the latest one is called WMV10) don't have much in common with MPEG-4 anymore, but use Microsoft's own video encoding technologies instead.
If you want to know how to convert .wmv files into other format, we recommend reading through our TMPGEnc XPress tutorial and also visiting our discussion forums for more assistance.
Relevant Guides:
How to play WMV files
Convert WMV to DVD-R using ConvertXtoDVD
Convert WMV to DVD-R using WinAVI
How to Convert WMV to DVD with DVDSanta
Using AutoMKV to create WMV files
Stream videos to Xbox 360 with TVersity without converting to WMV first
