> > Was the database created using TP9 itself (not imported from an older version) and are the files involved smaller than your setting for Options | Prefs | Thumbnails | Max file size for MD5 computation?
>
> First many Thanks!
> Yes it was created using Version 9. I just set the max file size to 2147483647kB.
> No result... any other idead?
What that MD5 setting does: When a file is larger than the specified size, and you create a thumbnail for it, ThumbsPlus won't calculate and save an .MD5 checksum for it (because that would take too much time and slow down the thumbnailing). This .MD5 checksum is used to see if files are identical.
When you change this setting, as you have, it will only affect future thumbnails. Your current thumbnails of large files still won't have an MD5 value until you re-generate them. Once you have done that, I'd expect the program to find identical files without problems. So, if you still have that test folder with identical images, just select them all and make new thumbnails (Ctrl-A, F3) and see if it works any better.