The storage device used in connection with an information processing apparatus is provided. The storage device includes: an authentication storage area storing an authentication program in advance, wherein the authentication program is executed to authenticate whether each user operating the information processing apparatus is an approved user; an operating system storage area storing an operating system in advance, wherein the operating system is encrypted and is used by the information processing apparatus; an access controller configured to control accesses the authentication storage area and the operating system storage area from the information processing apparatus; and a decoder configured to decrypt the encrypted operating system, wherein upon notification of successful authentication representing that the user is authenticated as the approved user by the authentication program, the access controller allows an access the operating system storage area from the information processing apparatus.