The present invention provides an image forming apparatus that includes a first system and a second system, wherein the permission/prohibition of access to a storage unit provided in the first system is controlled appropriately based on a signal transmitted from the second system, and a control method thereof. To accomplish this, the image forming apparatus of the present invention includes the first system and the second system, and permits access to the storage unit only when executing a program that includes a predetermined process to activate the apparatus using an external storage apparatus.