Planning Units

I have been trying to change the planning units in Primavera 3.1 from hours to days. However whenever I try to change or copy from another project via the menus: tools, project utilities, copy, I consistently get a message "invalid project name", eventhough all names and characters match. I am lost, if anyone has a solution to changing the planning units from Hours to Days. I would be very interested to know.

is dificult to change once you srart. I suggest you make a new schedule using the correct unit, fragnet your old schedule activities, put them in the new, and use global change to adjust to the new units