A control method for controlling an image forming apparatus comprising interface means for enabling access to a removable storage device, said image forming apparatus being capable of executing, separately from a normal mode, a service mode, wherein the normal mode is a mode in which a general user performs an image processing with the image forming a apparatus using image data or document data stored in another storage device different from the removable storage device, and the service mode is a mode in which a service person performs maintenance of the image forming apparatus using data stored in the removable storage device, the method comprising:
- a mode switching step of performing switching between the normal mode and the service mode;
- a storage device detecting step of detecting whether the removable storage device is connected to the interface means when the mode switching step performs switching from the service mode to the normal mode;
- a normal mode inhibiting step of inhibiting switching to the normal mode when the removable storage device is detected in said storage device detecting step;
- a maintenance allowing step of allowing the service person to perform the maintenance of the image forming apparatus using the data in the removable storage device when the removable storage device is detected in said storage device detecting step after the normal mode has been switched to the service mode;
- and
- a warning displaying step of displaying a warning in a display/operating section of said image forming apparatus when the removable storage device is detected in said storage device detecting step in a case where an instruction to switch from the service mode to the normal mode is made in said mode switching step after the service person has performed the maintenance of said image forming apparatus,
- wherein said normal mode inhibiting step causes the display-operation section to display a warning prompting to remove the removable storage device.