I find this very sad and almost frightening. It brings back the scared feelings I had when I started falling away. Even after I finally walked away, I feared them, dreaded their suits coming to my door, dreaded seeing them on the streets.
I would just lovingly tell whoever confronts you (if it does comes up) that you love learning about truth and you do a lot of reading. Not knowing what your files were or your grandchildren or if your family is the kind that would overlook this horrendous sin, I can't really tell you what to say, but I would keep it very light and try not to act too guilty. Or, you could just lie and say, "Gee, I don't know who saved those awful files! So many people have used my computer lately...maybe it was the demons!"