Hi all
Just wanted to let you know that Microsoft does NOT have any solution to the known "compatibility issue" that occurs when trying to upgrade an older version of windows to windows 10 by using the windows 10 upgrade app - the app icon appears on the lower right corner of your existing windows version (e.g. 7 or 8) when you have updated the software to the required maintenance level (SP1).
I just talked to Microsoft technical support and was first guided to download the windows 10 ISO file from aka.ms/win10dk (the Danish version), but my later conversation with the very same technical support revealed that the problem is NOT really technical at all.
The installation from this ISO file only supports new installation, which in practise means that when trying to install windows 10 on e.g. vmware Fusion 7.1.2 the installation procedure asks for a new windows 10 license key, i.e. it is not possible to select an upgrade and use the existing windows 7/8 license key to upgrade to windows 10. So all the downloading and guidance by Microsoft was just waste of time.
The only solution according to Microsoft technical support is to purchase a new software license for windows 10 - i.e upgrade from windows 7/8 to windows 10 is NOT free if you run your existing windows 7 or 8 on a virtual machine (VM).
I personally run my windows 7 Home Premium on the newest Mac mini with vmware Fusion 7.1.2.
So the conclusion is that the problem is not really a technical issue, but a commercial of a kind and dependent on Microsoft's licensing policy when running windows on a VM (Microsoft does NOT want to manually convert your old/existing license key to windows 10 license key).
Best regards, Ari