I am sure that you have used Divx Converter. This converter can only support these formats:
* MPEG1
* MPEG2 (plug-in required)
* WMV 7-9
* DIVX 3-6
* AVI
* XVID
* MJPEG, Motion JPEG
* MP4
* MOV (if user has QT 5+ installed on their computer)
In order to convert DAT to Divx, use Super Converter (Freeware).