According to this Ars Article once a machine is upgraded with media creation tool and activated the w7 / w8 key is 'converted' to a W10 key. So I tried myself, I upgraded the pc with W7 to W10 using the media creation tool, after upgrade W10 was active. 

Then I made the ISO for my edition (home) and tried a clean install. Result: installer refused the key. So I selected "ignore" and went on installing, then when finished it asked for the key again, put it, nothing "this key doesn't work", I put the generic windows 10 key and it continued but then it was inactive as generic key is blocked and doesn't let me change key, and anyway the W7 key is not working. So how are we supposed to reinstall w10 from scratch in case needed if it always needs to be upgraded from w7 (example) when it won't be free anymore??? This is a MESS.

This is just the 2nd day since the release of Windows 10.

When dust is settled, it is very likely Windows 10 product keys will be released.

If you have not done so yet, I would suggest that you burn the ISO to a bootable media such as DVD or USB.
Together with the yet to release product key, you can use the bootable media for reinstall in the future.

What yet to release product key? What are you talking about? There is not any product key arriving to you magically. The upgrade sets a generic w10 key and keeps the old w7 / w8 key in the registry. If you run produkey on your pc you will see two keys, the w10 (generic one) and the old w7 or w8 key being labeled as "internet explorer" and that's it, that's your key.

Clean Install requires a valid product key to activate. That is what I am talking about.

You " generic " Win 10 product key fails to activate. Meaning you do not have a valid Win 10 product key.

Good luck.

Someone else will come along to assist you.

Wow. Did you read the first message at all??? I know the generic key won't activate it. Oh Lord! You are missing the point COMPLETELY.

• Edited by Chriz74 14 hours 33 minutes ago

With a bit less intensity than Chriz, I must agree.

I have read that Windows 10 does support a fresh installation after the upgrade of the current eligible Windows OS (i.e. Windows 7, 8/8.1).  My understanding is that after performing the in place upgrade, and allowing Windows to activate, your existing Windows 7 or 8/8.1 key is now valid for that copy of Windows 10.

I followed this procedure and upgraded my Dell workstation from Windows 7 SP1 to Windows 10, which worked perfectly, and activated.  I then booted to the Windows 10 ISO I downloaded from Microsoft to do a fresh install, but at the beginning of the install it asks for a product key.  I used my existing product key that was registered with my Windows 7 OS that was upgraded to Windows 10, but the Windows 10 install is rejecting my key.  I have verified it is the correct key, but Windows 10 will not accept it.  Since this key that was part of the upgrade process is now supposed to be registered with my copy of Windows 10, I believe it should be accepted.  I have no other key to use.

I believe something in this process is not working properly, and is broken.  I have found no other solution yet.

The process may be broken, however it may be working like all upgrade keys have worked in the past. Say for example I upgraded from vista to 7 with an "upgrade" copy of 7 I bought from Microsoft. So long as I perform an upgrade and the upgrade sees a previous valid license it will take the new license. But if I were to try and use the Windows 7 ISO to do a fresh install, the key would be flagged as invalid.

This is because Upgrade cost less than full purchases, and therefore eliminates the possibility of buying cheaper upgrade versions and doing full installs. But then again, this is day 2 and it may not be working as intended.

• Edited by Acreed02 12 hours 42 minutes ago

The difference is that you were given an upgrade key. We don't have any here, we must rely on our existing w7 / w8 keys.

Do an upgrade install first to get the new key and then do a clean install.

Jerry

Clean Install requires a valid product key to activate. That is what I am talking about.

You " generic " Win 10 product key fails to activate. Meaning you do not have a valid Win 10 product key.

Good luck.

Someone else will come along to assist you.

No it doesn't. Once you perform the upgrade install and verify that Win10 has activated, your system is registered with MS. Do the clean install, skip the product key, and it will finish and activate just fine without.

With a bit less intensity than Chriz, I must agree.

I have read that Windows 10 does support a fresh installation after the upgrade of the current eligible Windows OS (i.e. Windows 7, 8/8.1).  My understanding is that after performing the in place upgrade, and allowing Windows to activate, your existing Windows 7 or 8/8.1 key is now valid for that copy of Windows 10.

I followed this procedure and upgraded my Dell workstation from Windows 7 SP1 to Windows 10, which worked perfectly, and activated.  I then booted to the Windows 10 ISO I downloaded from Microsoft to do a fresh install, but at the beginning of the install it asks for a product key.  I used my existing product key that was registered with my Windows 7 OS that was upgraded to Windows 10, but the Windows 10 install is rejecting my key.  I have verified it is the correct key, but Windows 10 will not accept it.  Since this key that was part of the upgrade process is now supposed to be registered with my copy of Windows 10, I believe it should be accepted.  I have no other key to use.

I believe something in this process is not working properly, and is broken.  I have found no other solution yet.

NO, a Win7/8 key will never be valid for anything other than Win7/8 respectively. Once the upgrade is finished and activated, your motherboard information is stored in MS servers as an activated Win10 system. Period.

Now, let's look at historically how things worked. If you installed Windows without a product key, it WILL still activate - as a trial. (Reads "not activated" with a usage timer)

This still occurs with the Win10 clean install, without the product key, the activation sends the motherboard info to MS, who responds with "Yes this system is licensed" and the activation succeeds.

The process may be broken, however it may be working like all upgrade keys have worked in the past. Say for example I upgraded from vista to 7 with an "upgrade" copy of 7 I bought from Microsoft. So long as I perform an upgrade and the upgrade sees a previous valid license it will take the new license. But if I were to try and use the Windows 7 ISO to do a fresh install, the key would be flagged as invalid.

This is because Upgrade cost less than full purchases, and therefore eliminates the possibility of buying cheaper upgrade versions and doing full installs. But then again, this is day 2 and it may not be working as intended.

Not true. You can certainly perform a clean install with DVD/USB of an upgrade copy. It only requires the upgrade to have taken place on an existing licensed system. All Windows versions send the product key and motherboard info to the activation servers. If the key has never been used, then it adds the two pieces of information to the database. If the key HAS been used, it checks to see if the motherboard information matches, and if it does, it activates.

In your Vista-7 example, your Vista key and motherboard are on file with MS. When you perform the Win7 upgrade, with the upgrade license key, the Vista key is replaced with the 7 key. As such, when you clean install with Win7 DVD, using that key, it matches the information on file and activates.

Absolutely not. The installer asks the key at the beginning, you can skip it but then at the end of installation it asks again and without a key you won't go past the screen. The w7 key doesn't work there. The generic one doesn't solve the issue. Microsoft has to clarify this. As I recall at first when w8.1 was out one couldn't clean install it without passing through w8. If what you say is true then MS has a big mess coming. Lots of people trying to install w10 somewhere sometime being asked for a key (they don't have). If the key is not necessary (but in reality it is) then why ask for one in the first place? I think neither MS knows. Obvious scenario after one year: try clean install. Keys don't work? Go back to w7/w8 or install a pirate w10 copy.

• Edited by Chriz74 27 minutes ago

You didn't read anything. You DON'T get any new key.

This maybe work in systems that have a w8 key in the bios but it's not working at all in non OEM systems.

So what happens if my motherboard dies with win10 and I need to reinstall win10 in a new machine? How Microsoft (or me) would ever figure out that I am allowed to do that?

Or do I need to go through the whole upgrade chain again?

Which, keep in mind, might even be impossible, if by that time win 8.1 for example is not supported anymore, i.e. will not be present in the store.