Saving as a .AVI File

I can’t seem to save as an AVI File, every time I press F3 to save, up pops a dialogue box stating:

ERROR:Select an image type in DisplayButtons(F10)

But I have set the box to AVI, what is happening

F3 is for saving a rendered image, not a movie. Just enter the filename and path in the first entry of the output panel, select the avi type in the format panel and press anim. This is all in the docs at