This computer data protection method of the present invention requires a user to enter a correct password for modifying any data. If wrong passwords are typed, this method forbids modification of any program modules. Further, if any program module is detected having unauthenticated modification, that program module is deleted and an original image of that program module is loaded to recover normal operation of the operation system. Additionally, a common password is also provided in the protection method. Some special function can use this common password to pass the detection of this method to perform any modification.