Learn first, do second. You're trying hard to get yourself in trouble by going where you have never gone before. The system refused to let you copy the file as a hint to get a clue first.

If you insist on blastin' around your files without learning some basics first people aren't going to feel inclined to spend their time bailing you out when Bad Things happen. Come back and ask your question about the prefs file after you've made an effort to learn some basic linux concepts.