The file then opens but the details are about 2 years out of date - the last two years' data isn't there.
Sounds like you are opening a different copy of the database file that isn't up to date. I'd do a search of your system for any other copies of this file to see if there's another copy out there to open.
Opening 'course registration' as read only.
The file was write proteced - you may not be able to make changes.
If this is a windows system, right click the file and select properties. You should see an option that makes this file right protected. This can also be a setting "inherited" from an enclosing directory. You may need to move the file to a different location in order to remove the write protection.