Stephen Porter wrote:

Would it work to just make a copy of the current .PST file in another
location and then create a new data file inside Outlook that
references that copy. And of course choose the correct (new) file
format? Then I could change the default mail location and then
close the original one?

A data file IS a PST. You can't create a "reference" from one PST to
another.

You have to create a new PST in the correct format, make it your delivery
location (if you're currently using a PST as the delivery location), and
then copy everything from the old one to the new one. For the non-default
folders, you can copy the entire folder. For the default folders, you have
to open each and copy the contents to the corresponding default folder in
the new PST. When you're done, you can close the old PST.
--
Brian Tillman