Yeah, I think you should open it in the designer and at least SEE what is in there. How you will fix it really depends on how that was set up.
But I can't help thinking there's probably already a way to give this capability to your users without this R7-era page. Something built into Domino. Unfortunately, my current client base doesn't use webmail/calendar, so I don't have a frame of reference. But I suggest you look in the Domion Admin files for something about that. It should be a standard functionality.