An error message occures if you try to downgrade to Windows 7 on a Windows 8 device via Windows 7 recovery media.
As result of this problem the downgrade is not possible.
To downgrade from a installed Windows 8 OS to a Windows 7 OS, using a Windows 7 recovery media, follow these steps:
1) Boot unit and press F2 to get into BIOS
2) Go to “Security” tab and disable “Safe Boot”
3) Go to “Advanced” tab, select “System Configuration” then change boot mode from “UEFI” to “CSM”
4) Press F10 to save changes and exit.
5) Boot unit from recovery media (Press F12 on bootup to boot from USB or DVD media)
6) At the first screen prompt during recovery, double click on the top left hand corner to open a command prompt
7) At the command prompt type in the following 4 commands:
– Select disk 0
8) Type “exit” to exit out of command prompt
9) Follow recovery screen prompts.