Windows 10 upgrade for a day but now cannot roll back problem

[daristan]

Windows 10 upgrade for a day from win 7 but now cannot roll back. It prompt:
We are sorry, but you can't go back.
The files we need to take you back to a previous version of windows were removed from this PC.

There is still a folder called windows.old which more than 20gb.

 

[crimsonrain]

I also got this, end up have to use the windows 7 startup disk to save it aiyooo

 

[daristan]

Think using the disc , cannot roll back

 

[tungsten2]

Windows 10 upgrade for a day from win 7 but now cannot roll back. It prompt:
We are sorry, but you can't go back.
The files we need to take you back to a previous version of windows were removed from this PC.

There is still a folder called windows.old which more than 20gb.

How do you perform the Windows 10 upgrade in the 1st place ?
Maybe you can share so that other will learnt for it.