Doesn't Steam allow you to install to a direction of your choice? The name of that path alone is 62 characters long and although any of the subsequent original files would still be way under the 260 character limit, long film names may go past that. Of course that depends on your habits of filming and naming the films.
Also, if you have your Settings folder copied over the installation, you might want to check the contents of it. In my job I've often encountered that a personal folder can contain even multiple copies of itself inside each other. I have no idea how the customers have managed to get a copy of their entire profile under their Pictures folder, not to mention that inside the Pictures folder of the copied profile is another copy of the profile, again containing a copy of Pictures... Unnoticedly pressing CTRL while dragging files with the mouse or a glitch in a photo organiser, I really don't know. Anyhow, such things can happen.
