Recently I wanted to enable USB debugging on my new Moto E. But corresponding driver was missing which i needed to manually download. You can find the complete solution in following link
So the downloaded jar was Motorola_Mobile_Drivers_64bit.msi.img. It is not really a .img file. It is infact a .msi file. So I wanted to rename the file and execute it. But with normal settings windows does not allow you that.
So you need to do some settings so that you can edit the file extension.
In your Windows Explorer go to Organize -> Folder and search options. In that navigate to View tab and check uncheck Hide extensions for unknown file types.
Now when you rename it file (F2) you should also see the .img extension. Simply rename it and save (Enter).
You will get a prompt whether you really want to change the file name. Click on Yes.
And you are done. You file extension should change. You can change it to whatever you like. I mean always know what you are doing... you may make some application unstable. Also never mess with system files unless you know what you are doing.