I have a large, very good video quality AVI file. Trouble is that it
was obviously filmed in 16:9 but it is showing in WMP as 4:3, so it's
all squashed in the horizontal direction. How do I get it to show in
16/9?

Do I need to convert the file or just use a different viewer. I've tried various options on WMP without any luck.

Hi
The best option would be to use another player.
I don't use WMP to watch video, but you can have a look at this link and to the 5th question, maybe you can solve it this way:

http://www.microsoft.com/windows/win...vice/0075.mspx

Thanks, I followed those instructions, but unfortunately there is no "Display" in the Device list, and therefore no "pixel aspect ratio" to adjust... (thanks microsoft)

I have the same problem with DIVX player, RealPlayer and BlazeDVD, that's why I thought I had to do something with the AVI file itself.

Try VLC media player. It's free and will play anything. Just Google it.

Excellent, it works!!
The only player I've seen which allows you to choose aspect ratio.
Thanks!