I just downloaded the trial of Vegas HD. You can render as WMV which allows you to customize all the settings on the Video tab:
When I try to change the WMV frame rate to 23.976, I get this error:
“The custom template you selected is not valid with the current project settings. It has been removed from the template list.”
But I obviously can’t set the project settings to 24p. Any idea how to get it to allow me to render with these settings?