Hey DiDA:)
I had the same issue as you. My copy of windows 7 wasn't "genuine".
On MMOGA I bought a Windows 7 Pro Key for $25 which is basically dirt cheap.
I then updated windows 7 all the way to the current version, and then the "Get Windows 10 App" showed up
in the bottom right.
http://www.mmoga.com/
Hope this helps, let me know if you think there's anything I could do.
Also, on this page there is a troubleshooter that you can download and run, it will tell you exactly what updates you are missing, and also provide you with a link to the correct download!
https://support.microsoft.com/en-us/kb/3081048
I got Windows 10 running now, and am dual booting Mac OSX 10.10 and Windows 10 using the latest version of Chameleon.