I have had the same problem with my HTC TP2 Windows Mobile phone. I set the Outlook Calendar parameter for "last 3 months" in the Windows Mobile Device Center, thinking that the phone would only download 3 months of historic calendar appointments, but instead it deleted all but 3 months of appointments on my Outlook calendar in my computer. I also use the calendar for recording things that I do not want to lose. Is there any way to retrieve those historic appointments that have been deleted?