Windows 10: How to get product key of old OS (Win 7) after upgrading to Win 10?

You are correct, you do not tolerate being corrected.

That was the EXACT situation the OP was asking about when you posted your nonsensical statement that said it wouldn't do the OP any good to retrieve the previous OS product key. The the above statement is incorrect anyway, the Windows 10 will remain activated, if it remains installed, and the previous OS Product Key is used to reinstall the previous OS in a dual boot situation. Many members of this forum have done exactly that and both their Windows 10 and their previous OS on a separate partition are activated - although in violation of the EULA.

 

To come back to the original question: After the upgrade to Windows 10, you have a 30 day period to go back to the previous version of Windows. The question now was whether - after these 30 days were over (and the previous version had been removed from the PC) and if you then went back to the previous version, if then this old version would still (meaning: again) activate.

The answer is: Yes, the old version of Windows will activate again. The old key can stil be used for the old version:

From Recovery options in Windows 10 - Windows Help, section "Go back to your previous version of Windows"

 

Just started a clean install of Windows 8.1 Pro on a PC the had done the free upgrade to 10 Pro. 8.1 was originally installed with one of my MSDN keys. Several clean installs were done on that PC with that key before the upgrade to 10 Pro. My key is entered via a PID.txt file during the install. It's at the copying files part right now. Key has already been read as far as I know. Will have to wait for it to finish and look at the system screen.

 

Ok install finished system page shows "Windows is activated" as I knew it would. I don't know what Kari is doing to mess up activation, but I had no problem going back to 8.1 Pro from 10 Pro. That 8.1 pro key was well used too, only ever used on that one PC though. I've seen several other threads where people have gone back to the previous OS via a clean install with no issues also. Other than finding the correct install media that is.

 

Reusing the same product key in a short period of time across multiple computers will get that product key banned from online activation, but it can still be used for phone activation. In my days of beta testing Windows I had product keys that were blocked from online activation but could be used with phone activation. Then after about 6 months of non-use, the product key would activate online again.

 

Anyway, to get back on track. As mentioned, OEM keys are not stored in the BIOS for factory Windows 7 OEM installs. All that is in the BIOS is an OEM marker in the SLIC table. Even if you retrieve the OEM key from the Windows registry, its useless without the matching OEM install media that has the certificate file on it. Try to use it with normal install media and it will fail activation. You can't phone activate that key either. You need the key on the COA sticker to do a clean install with normal non OEM install media. If the Windows 7 install has been wiped by a clean install of a new OS, so has the key that went with it, OEM or not.

 

Yeah, I'm very careful to keep track of what keys get used on what PC. Windows and office etc. I've done a bunch of clean installs with my MSDN keys with absolutely no issues.

 

There are ISOs available that OEM Windows 7 keys can be used with.
Download Windows 7 ISOs, Legally and for Free | PCsteps.com

It is ridiculous that Microsoft won't let you get a Windows 7 ISO for use with an OEM key.

 

I just confirmed it myself. Well past the 30 day period, did a clean install of the previous OS, Windows 8.1 Pro, activated just fine.

 

The key on the COA sticker yes. The factory OEM-SLP key requires custom branded OEM install media. It has custom OEM files on it to do the OEM-SLP activation.

EDIT: My MSDN Windows 7 ISO will accept OEM and Retail keys. By OEM I mean the ones on the COA sticker.

 

K. My Home Premium keys are coming back as OEM:NONSLP on showkey.

 

Yeah, the OEM-SLP keys are generic keys common to that manufacturer. They are actually blocked from online activation and phone activation. Factory OEM-SLP installs do not activate online, they activate against the SLIC table in the BIOS. That's why the key on the COA sticker is a different key and a unique key. It can activate online, although I've usually had to do a phone activation the first time I used one of those. If you can actually read the sticker that is.

 

No, Kari. I respect so many of your posts, but in this case you are very very wrong. I have, on several occasions upgraded an OS to 10, and then reverted back to the old OS by reinstallation and re-activation. The key is fine, and continues to work. It is not flagged as "used".

If you use the same key to activate too many times too quickly, it will be blocked from online activation, saying it's already in use, but you are free to use the phone activation to re-activate.

This doesn't really even make sense, since upgrading only uses the activation certificate from the old OS and activates based on that. It may contain the old key in that certificate somewhere, but it does not in any way invalidate the old license.

Of course, you're not legally allowed to run two copies of the OS at the same time, but that doesn't change the fact that you can do it.



Of course I could have done the last install with a generic Windows 8 key and then try to activate it from the settings, but the result is the same: key is used.

I repeat the fact that the Windows 8.1 Pro key I used for this experiment was virgin, never used before. Those knowing MSDN, I only claimed the key today just before starting this experiment.[/QUOTE]

 

Uhoh Mystere.... Kari himself said:

 

Yes, I said that. Tells quite a lot about you that you had to post about it without any whatsoever context, just for insult's sake.

Now I am acknowledging the fact that MS seemingly has somewhat lenient policy regarding Windows 10 upgrades and I was wrong in this matter; I have now repeated my test two times, both times installing and activating Windows 8 Pro with a valid retail key on two separate machines, then upgraded to 10 and tested the key again on a third machine, this time the reuse of the key, activating Windows 8.1 with the same key used for upgrade had no issues.

I have no idea why the key in my first test stopped working after the upgrade, I could not get it to work today even with phone activation option. Also, my previous experience with the Windows 7 Ultimate key as told previously in this thread, together with some other facts and some logics makes me to believe that the way it seemingly works for now might stop working at some point.

I honestly believe that it should not be like this. I believe that the intent of Microsoft was and is not to give every owner of valid Windows 7 and 8.1 a second, another operating system for free letting users activate a qualifying previous OS on one machine and the free Windows 10 on another, but instead let users of Windows 7 and 8.1 upgrade, replace their previous valid and qualifying OS with Windows 10.

Simply, the intent of Microsoft is quite clearly that a user of a qualified OS uses the upgrade on that machine, replacing the previous OS.