After you open a project in iDVD 6 that you created in an earlier version of iDVD, an alert indicates that photos used in slideshows, backdrops, or drop zones are missing. You may be prompted to locate the missing items.
To prevent this issue from occurring, update to iDVD 6.0.4 or later.
If you have an affected project, you have two options:
Tip: If you have opened this existing project because you want to burn another copy, and you don't plan to make any changes to the project — remember that you can also make a copy of this project if you have a DVD of it that you have previously burned. See "How to copy previously-burned DVD-R video discs" for details.