I assume you are capturing your video to the pc via firewire and selecting DV as the capture format, is this correct.?
When you use this method the video from the camera is literally copied/transferred to the pc. What you have is what you get DV-Avi. if the camera recorded using 16:9 then that is what you get.
Read my guide Dv-AVIhttp://lata.me.uk/video_studio/guides/q ... de_avi.htm
From the timeline Right click one of your clips and select properties what are they?
There seems to be some confusion regarding the aspect ratio, can you give property details of all the different types of video you are using, right click each type. If you have two types then which one do you wish to use 4:3 or 16:9, I assume you will want to use widescreen 16:9
Carroll, what are you trying to make?
You indicate You Tube, but are you also wanting to burn a DVD?