From iA wiki
The first version of DivX was called DivX ;-) and came directly in version 3. DivX ;-) was not developped by DivXNetworks Inc, it was a hack of the Microsoft's pre-MPEG-4 video codec allowing it's use in AVI files. Since version 4 DivX is named DivX without the ";-)" and is no more a hack of a Microsoft codec.
- Divxstation.com - Articles and subtitles for Divx.