Rendering out a 1080p AVI for delievery to a client and though I can drag the rendered AVI onto the timeline it won't play in WMP and only plays like the first 10 seconds in VLC. Just using the default HD 1080-24p YUV. Need to make sure that the client can open it!
The avi.sfl file is created by Vegas when you render. I think it may have to do with audio, in the same way that .sfk file are used, but I have no idea. I don't think its of any significance once rendering is complete.