Im afraid my friend knows my windows 10 retail key. how can i restrict him or anyone from using my windows 10 key. i have signed in with a microsoft account but im not sure if my Microsoft account is linked with my windows 10 key. Will Microsoft send me an email if someone tries to use my windows key? How can i make it more secure like an email account? Can i set a mobile number on which i can get an OTP, in case i forget my activation key or someone tries to use my key?