1. A method of executing an additional extended feature of an image forming apparatus including a display unit and a plurality of operating systems, the method comprising: receiving a program indicative of a computing environment realizing the additional extended feature from an external storage medium; establishing the computing environment realizing the additional extended feature by installing the received program; receiving an application from the external storage medium, the application corresponding to the additional extended feature differing from a native feature basically supported by the image forming apparatus; installing the received application using one operating system of the plurality of operating systems; selecting the additional extended feature from a menu showing at least one application installed in the image forming apparatus displayed on the display unit; and executing an application corresponding to the selected additional extended feature using an operating system corresponding to the selected additional extended feature, wherein the plurality of operating systems are executed on a virtual machine and include a real-time operating system and a non-real-time operating system at the same time, and the image forming apparatus comprises at least one of a printing module, a scanning module, a fax module, and a copy module.