Excel File locks for editing!!!!

We rebuild a couple of systems with windows 2000 professional and we also installed office 2000, they have SR 1a and service pack 3 for the OS and for office. When they open an excel sheet that is saved on the shared folder on a 2000 server. They get an error the the file is locked for editing by them, or by one other user. But the file is not being used. I’ve closed the app, open it as read-only then save as to their local drive and save it back to the share drive with different name, they areable to open it and close but when they try to open it again they get the same error. Need some help thanks.?????????