Crystal Reports screen view help

Message

     I'm very new to crystal and have an issue that's possibly caused by me or there is a simple fix (I hope).

when I open crystal both the screen design and preview panes should be available.  But some reports only have the design screen making it difficult to see the finished report.

all my reports where created in the same way so why does the preview pane only open in some of them.

Thanks
Melanie