How do I uninstall Windows 8 and install Windows 7?

I have a friend, who just got a new Toshiba Satellite C series with Windows 8. I tried to uninstall Windows 8 and install Windows 7 but was unable to do so.

I did everything I could:

1. 
   

   Boot disk - would not load (error message Media -- Fail)

   
   


2. 
   

   Boot USB - would not load (error message Media -- Fail)

   
   


3. 
   

   Loading Windows 7 disk from system, fails with different errors

   
   

Does anybody know what I can do in order to install Windows 7?

Answer

Toshiba explained all steps in a KB article:

Steps to Install Windows 7 on a Windows 8 Unit

http://aps2.toshiba-tro.de/kb0/TSB2B03EX0002R01.htm

If a Windows 8 OS was preinstalled on a notebook, some steps are necessary to prepare the notebook for a downgrade to Windows 7 OS.

 1. Changes in the UEFI firmware
 2. Boot a Windows 7 recovery media
 3. Change manually the partition table

1. Boot unit and press F2 to get into BIOS, go to "Security" tab and disable Safe Boot. Go to "Advanced" tab, select "System Configuration" then change boot mode from UEFI to CSM. Press F10 to save changes and exit.


2. Boot unit from recovery media (Press F12 on bootup to boot from USB or DVD media)


3. Press Shift+F10 to open cmd, run diskpart and run the commands from the picture