Marcelo,
I think you might not understand how FOG works. FOG for imaging is only used to image a computer, similar to Norton Ghost, Acronis True Image, and Clonezilla. FOG will not aid in installing an operating system other than deploying the image onto the drive. If you want to add an option to boot Windows 7 into a “silent mode” this would need to be entered into the answer file when you created it using WAIK. All the settings would need to be configured here, and then the host machine imaged with FOG.