You are making a mountain out of a mole hill here. If, I said if, the NSA was really interested in what you are doing on your computer they would go to your ISP and ask for your records. Your ISP keeps copies of every email that you have ever sent. And copies of every email, this one included, that you have ever received. They also keep records of every site that you have visited. What day and time and how long you stayed. What files you have downloaded. Maybe a pirated game? Maybe pirated music files. Maybe a little p0rn? Many things. And if the NSA really did want to see what is on your HD they would walk in and take it with them when they left.