You can use Virtualdub (free)
To rotate AVI video files in VirtualDub:
Taken from another source
* Open your source video
* Click "Video->Filters" in the menu
* Click "Add" and select "Rotate"
* Choose whether you want the video rotated left or right (it will show you a preview if you're unsure!)
* Click "Save as AVI" (choose a different location or filename as it won't let you overwrite the original fil