I now know what happened on that machine of mine. Turns out my colleague started the installation behind my back, whilst I wasn't looking for 2 mins. He made me believe that I had started it. crap.... Sorry for this thread, I guess it was kind of pointless then. I got home and on one of my home PC's it is as you guys say. If I don't do anything I don't get prompted to install it. On my HTPC I started the installation via the icon in the systray (Get Windows 10). So it looks like you aren't forced to eventually install it anyway.
On the PC here I did not go through the "Reserve my copy". When I checked in the Windows Updates the only update listed was Windows 10. If I close all the Windows and go to shut down the computer there was only the option "Shut down and install updates". I can lock the screen and then I would have the option to either shut down or shut down and install updates. I ended up installing Windows 10 and after a few steps I had the choice to either start installing now or postpone the installation. However the postponing only allowed me to postpone it to a maximum of 3 days. I ended up installing Windows 10 straight away. What I was wondering is, if this is the same behaviour when you reserve it then all my family with Windows 7 will essentially be forced to install Windows 10, or actually end up installing it inadvertently when they next shut down the PC. You are correct, it did all of that. What was bothering me is that it was being listed in the "Shut down and install updates". After you go through those steps you will still see a final message where you can install or postpone the installation, but you can only postpone it for three days and I don't know if you can then postpone it again after that. Anyway, at home I have a PC with Windows 8.1 where I reserved a copy, I'll see how it works there.
So a lot of computers started having the Windows 10 upgrade available, but so far it is being forced on the machines, at least from the ones I have seen. The few computers I have here only have the option to shut down with installing updates. Is there any way of restarting computers or shutting them down without installing the Windows 10 upgrade? I don't want to completely get rid of it, just wait a few days.
I also don't like it. I'd rather be notified and install the updates when I choose. The past years Microsoft has been releasing quite a few buggy updates that caused lots of issues. This is why I'd rather wait a couple of days and then install updates instead of getting them on the same day, as soon as possibe.