Trying to install Windows 7 with Boot Camp

[carlsson]

iMac 27" 2011.
Original HDD replaced with Samsung SSD 1 TB.
Updated to macOS High Sierra.

I want to install Boot Camp with Windows 7.
I have an original Swedish Windows 7 Home Premium DVD.
When I open Boot Camp Assistant I get the usual window with two checkboxes; "Get drivers" and "Install Windows 7 or 8".
I check the boxes, it fetch the drivers but then it stops saying "Windows 10 may not be installed on this computer".
But – I don't have a Windows 10 DVD, it's a Windows 7 original MS disc!

Any ideas?
[doublepost=1513522483][/doublepost]One more restart and the problem vanished.

Thanks.