PPpad works with lines of the text, not with a file names. It doesn't split path to drive + path + filename and evaluate it. You can remove drive letter or path before sorting and removing duplicities
Or you can write PSpad script extension, what will take all lines in the file, split it into file path parts, sort it and remove duplicities as you need -- <https://forum.pspad.com/read.php?2,79444,79445> PSPad freeware editor https://www.pspad.com
