In order to export your video edit to a new AVI file, you need to:
- Set your Render Settings to a movie format that supports AVI
- Click the Render Animation button.
As long as you have the Sequence checkbox selected in the Post Processing panel, it should render out your video edit to a new video file.
There are a number of Movie formats that also support the AVI encoding format.
- AVI JPEG
- AVI Raw
- H.264 (with AVI format selected)
- MPEG (with AVI format selected)
- Xvid (with AVI format selected)
Source : blender stackexchange and 15thDimension