I think i'm just being a little cautious as I have never moved data from
one
calendar to another before and would hate to lose anything.
Make a backup by copying your PST to a second folder. Be sure Oultook is
closed when you do. If you install Outllook 2007 over the top of Outlook
2003, the installer should detect the prior version and allow you to
upgrade, making all your data available in the new version. It doesn't
always work correctly, though, so you may have to start with a new mail
profile if the old data isn't there.
I have read that in some cases the data would be transferred in blocks of
Ten years which could mess with Birthday dates. (maybe ref was to do with
a
different calendar)
Where did you read that? It's simply not true for Outlook.