When would a copied disc not be identical to a source disc?

The copied disc will not be identical to the source disc if any of the following occurred:

(1) You compressed the video to fit the source DVD movie content onto a blank DVD disc,
(2) you removed some unwanted content from the source DVD movie or
(3) the source disc contains other data beside the DVD movie. PowerDVD Copy will not copy any applications, pictures or text files stored in the source DVD. PowerDVD Copy will only process and copy the DVD movie content.