Click on File -> RenderAs. Then, after choosing the type of rendering you want to do (e.g., MPEG-2, WMV, etc.), click on the "Custom" button. Click on the Video tab and, depending on the type of format you are rendering, you should find a control that lets you set the bitrate.
Do you mean to tell me that you cannot alter the bitrate while rendering? I always thought that the bitrate had something to do with the quallity of DVD. Why does MainConcept give you that option, then?
OK, thanks for the explanation. I'm having a lot of trouble trying to get a good burn on a DVD and have been messing around with the bitrate. I've got stills which have to be progressive and DV which is interlaced and I can't get a good combination of settings to render with.