[DaltonST]

Another thought: look in C:/Users/Steven/AppData/Local/Temp/ to see if any .pdf files are in there. Obviously I am grasping at straws, since there is nothing that I can see (without actually sitting at your PC) that is wrong. I'm looking for a clue to exactly what is wrong.

Can you create a collection outside of AppData, like in your Documents folder, and try exporting that?

Is Calibre in your PATH? When you installed Calibre, did you tell it to do "everything", which it does by default, or did you say "no" to adding Calibre to the PATH?

If you were NOT an Administrator when you installed Calibre, perhaps the PATH is not correct. Windows security is a pain. Open a Command Box, type "path", hit enter, and check for Calibre in the program directory.