Sorry for the hassle, but I'm using Outlook 2007 and I can't find a way to follow your instructions below:

Open Calendar>Options>General Options>Scroll to Actions>Check the "Keep Appointments" field - set it to "Forever"

With calendar open, I can only find options by going through "tools" and I can't find General Options or any of the further locations you mentioned. Please advise if possible.

Thanks very much.