Problem with converting videos into my portable devices

I am having trouble converting my videos into my portable devices. I am tired of installing one specific software and then convert the videos onto a specific devide. I want the converting function all in one! I?m using another free downloaded convert software to do it, it works fine with the first devices. But suddenly it just shut down automatically, no matter how I re-operate it, it just won?t work. Any one can help??