Windows 10 has never come with a serial key. They have done away with all that. So if someone says to you I need your key to install 10, thats BS.

Thats something you will need to ask the shop.

Yep. If you brought the retail Windows 7 you an just transfer it. (So run Windows 10 setup using the links I gave you ealier and when it asks for a CD key, type your Windows 7 one in.)

Edit: You only need to do that the once. Once you register the key, it will remain registered to 10. So if you ever have to re-install 10 just skip key entry.

Yeah so if your in it for the long term, then OEM isn't really nothing to worry about.

Yeah, because if I understood him well, Pond86 explained that it should be possible to reinstall it, even with an OEM license.
Ahah, no problem, I can be badly formulating things too ;) And no problem too : solidarity is always nice to see :) So thank you again !

But.. When transfered/registered, and installed... The serial will be available for another comp' if I decide to ?

Huuuum.... We'll see what customer service says, and will think about it :)

You can use the older version the same PC. (Replace should you want to downgrade, and 10 will be free and waiting for you to come back. And from what people say set up a duelboot, though i've not tested that.)

As for another computer at the same time if its retail then i'm not sure, you will not be able to upgrade for free again using the same key, but as to if you could run that older os on another machine I can't say (though I doubt it.) Though if the serial is for a OEM version then its only for the older machine to get a free 10 upgrade (if it supports 10.)

I don't know if we'll do this, but not bad idea.

Okay, I think I understood :) We'll take a look at what version of Win7 she has, if it's OEM or not.
Thanks again for your help ! :)

Edit : we just tried your command line : I attached the screenshot (I blurred the 4 characters of the partial serial key).
I read OEM... this means we can't install this license of Win7 on another comp even if there's a product/cd key ? Oo

Licences are transferable, under specific circumstances. You'd have to call up Microsoft, and it could be arduous depending on your luck with the person on the line.

There exists NO "virtual" license for Windows 10. Windows 10 is genuine, or it is not. The way the license is managed by the OS/PC/firmware, though, is a completely different affair...

Likely, if you bought a "branded" (not custom built) PC, you have a "digital" license - ie one that doesn't need a product key to be activated by Microsoft authentication servers. It's the same as the one that came with my latest PC, and is permanent: once you activated it, it will be valid for every new Windows 10 (re)installation/update through the aforementioned on-line servers.

Oh, and forget about "transferring" it to something else than the PC it came with....

I was really confused when doing my researches ^^"
What means "genuine" exactly ?

So it's very certainly a digital license.
And so.. if I want to change my harddrive (because for example the current broke suddenly), can I reinstall this windows on the new harddrive ?

This really... astound me to hear that the possibility may exist, but that it's so much luck based :P

So, the end of the story.
And sorry for the approximate explanations who will be next ;)

We phoned to customer service, and they confirmed what was mostly said here by lot of you.
Mainly that it's mostly like before, but simply that we don't see a "cd key" on the tower : it's now your motherboard who "register/remember" your license (but there is still a product number, simply you don't see it), and so, yes, it's tied to your PC.
You can add components to your comp' or even change some, that shouldn't be an issue. Even the hard drive : you should be able to take a brand new drive and replace the existent one, and install a fresh windows from an image taken on Microsoft website : there shouldn't be issue, because it's your motherboard who "knows" the license.

But, just in case, you should be able to see your product key thanks to some software (like "ShowKeyPlus" they said). This way, if your motherboard dies, you still should be able to reinstall windows by providing the key manually.

Oh and yes, it seems that nowadays it's almost always that when you buy a computer with pre-installed windows, it's this way.
And price difference between OEM and retail license isn't that big in the store we used : several dozens of euros.

There shouldn't be issue for dualbooting with linux. They advised us to avoid dual boot with a too older windows version, because components may be too recent to be handled correctly.

So in the end, we keep the comp', and we are now about to discover the "marvelous world" of Win10. I will have to create a new thread about this adventure, we'll need some (& advices) :P

Thanks again for all the help folks :)

Since you seem to worry a bit about privacy I suggest you use O&O ShutUp10 (https://www.oo-software.com/en/shutup10) which makes switching off all known privacy invasions a breeze.

I have the same question, those serial numbers are so confusing

It sounds like it comes with a digital license, also known as a "virtual" license, for Windows 10.