For the sake of argument -- if you were talking about your real desk to someone, you would say "my desk", no? If you were talking about a document somewhere in your files, you would say "it's in my files". If you were forced to physically label a drawer of your personal documents either "my documents" or "your documents", I think it's safe to say "my" is the more intuitive choice there.

To me, "your" violates the human-machine boundary more than "my" in many circumstances because it implies the machine is its own autonomous being that has its own "my". No, the computer isn't giving me anything; I own the computer, and I own the files, there is no external exchange here.

(all that isn't to say there aren't plenty of cases where "your" makes more sense -- more than where "my" makes sense, by my reckoning, considering how often there is an external exchange of some sort going on. But "your" isn't a one-size-fits-all solution)