Yes, it is the correct file.
For more information on the img file please see:
http://social.technet.microsoft.com/Forums/en-US/projectprofessional2010general/thread/77e391b9-a894-4bd2-b4c9-8f9ded31b43a
and
http://social.technet.microsoft.com/Forums/en-US/projectprofessional2010general/thread/0749ae5c-42ae-4bc2-b866-39ec245c3400
and
http://social.technet.microsoft.com/Forums/en-US/projectprofessional2010general/thread/b13b43f7-51ae-4060-acf3-4dd339c2d89f