Advanced Tools - Collection Maintanace (?). There is a function to renumber your MovieIDs. But the function doesn't change the picture numbers, too! So you would have id 1 with the old cover name 24-movie-name.jpg. The equalize these you could use the plugin "CoverManager" - not to be confused with the inbuilt one.
In order to achieve what is possible, you have to try the impossible over and over again. Hermann Hesse
But there is some strange Bug in the "CoverManager"...
I just tested the ID-Prüfer Function. But even after all 3 Steps, reopening XMM the same function still tells me that there are many different ID's in BackCover and Fanart.
I looked in the cover Folder and the "CoverManager" renamed all Cover wrong! In all Filenames is the Title missing!
Very strange! Today I have processed my own database with and haven't recognized any bug. I will have a look at tomorrow before work. Maybe it's because you start it out of XMM? I always run the prog alone.
*Edit* Just tested it here @work. No problems. All filenames are correct as far as I had time to check.
In order to achieve what is possible, you have to try the impossible over and over again. Hermann Hesse