Try Air Playit. It can help you remotley play any video stored on your computer in iPad, even DivX, Xvid via WiFi, 3G, 4G networks. It can live convert videos to iPad incompatible foramts.
More information: http://www.airplayit.com/blog/tutorials/streaming-divx-xvid-video-to-ipad-iphone.htm
Actually you know iPad just can play .mp4, mpeg-4, h.264, etc. videos, so if you wanna play divx or xvid video, have to convert video into the certain format that ipad supports. Third program may help you a lot.
i personally used iMacsoft iPad video Converter tool, converts any videos, dvix, xvid, flv, wmv, avi, rm, etc. into iPad screen. Hope it helps you!