WMV

WMV stands for Windows Media Video -- developed and controlled by Microsoft.

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.