Editing EI.CFG

The EI.CFG file is a file that instructs Windows Setup on which edition it has to install (like Ultimate) and on which channel (like Retail).
You can find this file on some ISO images (you can also create it if it doesn't exist), open it with notepad.

You will then find a content similar to:

[EditionID]
Professional
[Channel]
Retail
[VL]
0

• [EditionID] is the identification of the edition, such as Professional, HomeBasic, HomePremium, Ultimate, Enterprise, Starter and more. If blank or not specified, setup will display every Windows edition available in the ISO image.
• [Channel] is the licensing channel, and can be Retail, OEM or Volume depending from the edition you want to install
• [VL] is a flag indicating the setup will install the GVLK key for your edition (only if [Channel] is set to Volume)

Here are also a bunch of reccommended configurations:

• Windows 7+ Starter, Home Basic, Home Premium, Ultimate and Professional Consumer:
  [EditionID]
  
  [Channel]
  Retail
  [VL]
  0
   
• Windows 7+ Professional, Enterprise Business/Workstation:
  [EditionID]
  
  [Channel]
  Volume
  [VL]
  1