If you have not changed the file names, locations or field data you can do the following:
- Restore your old library. (You may want to create a new empty library before the restore)
- Create a smartlist with this rule: ~d=cm (this will include the files in the Main and CD/DVD databases)
- Go to the smartlist and export it as an MPL file (File > Export Playlist, select "MPL" and "output range: all")
- Change to your new library
- Turn of the Auto-Importer (this is a precaution, I have not tested if this step is actually needed)
- Import the MPL file using this menu: File > Import Playlist (you must change the "Files of type" option before you can import MPL files.)
This updates all standard library files (audio, video, images, documents and files in the CD/DVD database) with the previous library field values (including the import dates and statistics).
You can check what info an mpl file contains with a text editor (it is better to export a separate small file list for this).
If your old library had custom library fields you must recreate them before importing the MPL file.
EDIT
You can also use the MPL file for importing the files to a new empty library and updating the "Date Imported" field values. In this case you just need to import the MPL file twice.
EDIT 2
It looks like the files that were previously only in the CD/DVD database end up in the Main database. The only way to keep them in a separate place after that is to create a new view scheme for them and use view scheme rules for excluding them from the standard view schemes.
If you don't want to include the CD/DVD database use this smartlist rule: ~d=m
EDIT 3
You can add a rule directly in the "Edit Smartlist" wizard if you press the Import/Export button and write or paste the rule there.
A feature request for JRiver:
Add a switch for importing an MPL file which has only CD/DVD files so that the files end up in the CD/DVD database.
Another request:
Change the name of the Import/Export button to Import/Export/Edit or something like that.