I need to know the name of a movie i saw a long time ago.?

What's the name of the movie where a women writer gets a male robot to protect her while he stays in a log cabin working on a new book. When she firsts gets the robot he is very basic. Then later she upgrades him to simulate emotions. The robot ends up falling in love with her and becomes really over pertective and ends up killing one of her friends and traps her in the cabin. She gets away using a near by lake.