Exporting Widescreen To Wmv

im having a bit of a problem here, the new video im making is shot in 16:9 mode (widescreen) and all goes well, editing and even exporting to new AVI, no problem but as soon as I try to export it as WMV things go wrong, it always ends up boxed, whatever I do really.

I could type in some kind of weird W x H size but it would give me quality loss I think. How do you guys handle with this?

if you use vegas 7 theres a wide screen setting.
What are you using to edit? does it have a wide screen setting?