Just use VLC. It will convert anything to anything. AVI is just a container for the codec
I don't recommend freeware, but I can share with you Video Converter which I used many time, not for free though. It's quite easy to do conversion in just three steps. Firstly, add DVR videos to the program. Second, select AVI as output format. Last, hit the “Convert" button. If you want to burn DVR to DVD disc, you can move to the "Burn" interface of the program, insert a blank disc and start ripping.