As shown in this picture, I have opened the P42DC locomotive file to only find this. There are many missing files here. This is also a problem for all my other locomotives as well. I have reinstalled many times, however nothing has seemed to work.
a lot of DTG packs use the .ap format like a .zip file, so your file are there, just inside that .ap pack If you want to see the files themselves (or at least a version of them) use 7zip or similar to unpack the .ap file into that folder