We have a Canon HD10 camera, which produces high quality material, but only in widesceen format.
There are occasions when we wanted to upload a video to a website which did not accept widesceen.
We read the manual thoroughly and also scanned this forum, but it still took us several hours to figure out how to do it.
In the hope of saving other people a lot of time, here is a method:
1. In Pinnacle Studio 12 Ultimate, Setup, Project preferences, Project format, Set from first clip added to project
2. Add a dummy clip of the desired format
3. Add the required 16:9 HD clips, they will come out as "letterbox" i.e. black bands top and bottom
4. Delete the first (dummy) clip
5. To get rid of the black bands (called "edge cropping"), for each HD clip
a) Double click the clip to bring up properties
b) Select "Add an effect to a video clip" (bottom icon in the properties, looks like an electric plug)
c) Add new effect, category Studio Plus RTFX, Effect 2D editor advanced
d) Press reset to remove default effect
e) Size H 129 V 134
f) Cropping total L+R=20, for centring L 10 R 10
You can apply the effect to several clips at the same time, but of course only if the cropping is the same.
A request to Pinnacle.....
Either a) tell us there's an easier way of doing it, or b) make an easier way, please! 
Janet & Nick
http://www.janetseclecticreviews.org.uk/