This strange Windows koan, er... error message must've been designed by a zen master! Found at project x3150 [Flickr] - via Look at This ...
The weirdest computer error I've ever encountered was: "Bad magic number. Seek bloody revenge." (An old *nix computer in college way back when - I don't even remember what I was doing but I'll remember that error message till the day I die!).
The Fieldata COBOL compiler for UNIVAC Exec 8 had a diagnostic that read:
Statement is vacuous.
Windows presents Choose Your Own Error! How exciting!
Also, the apparent tautology, "the filename exists or it doesn't" is false (though I am sure you are aware of that). The syntax of a rename command is usually rename filename1 filename2. When the error message says, "duplicate file name or file not found," it means that filename2 already exists or filename1 does not exist.