Improved approaches to update computer program code residing within a computing device are disclosed. By maintaining a former version of the computer program code, the computing device remains operable even if the update to the computer program code fails. Hence, the invention permits reliable updates to computer program code, which is particularly useful for firmware (e.g., boot-up code) of computing devices. For control and security, each version of computer program code can include authentication information. Before the computer program code is used, the computer program code can be required to be authenticated using the authentication information.