For disabling auto login see
See: Get rid of the windows login screen]
Warning: this will enable anyone to open you computer locally and if the user name is administrator they will be able to do anything to windows, malicious or other. This will NOT disable any security through the network, internet, or other remote logins, and will remain the same security as before. So the local computer will be insecure and the people seeing the computer remotely will remain as secure as without auto login.