Windows 10: W8.1/W10 dual use, same product key?

On my desktop I have a number of removable storage racks in which I can
slip disks in and out in cold swap fashion. This arrangement makes it easy for
me to use different versions of operating systems without having to deal with
the complexity of virtual machines.

Im running W8.1 Pro 64 bit on a SSD as my main production system. This SSD
hosts only the operating system and installed programs. All my data resides
elsewhere. I have cloned this SSD to another SSD which I plan to use to upgrade
W8.1 to W10 when W10 reaches my part of the world. Since I havent taken part in
the Insider Program, I need a few months to ascertain if W10 is worth using as
my main production system. During that time I want to continue using W8.1 as my
main production system.

My question is, will W8.1 still work after I have used its product key to
upgrade to W10? I guess W8.1 will still start but will it be able to receive
security updates after the upgrade to W10?

Many thanks for any insight.

:)

 

Activation problems after hardware changes and reinstallations.

So, originally I was using w8.1pro. Did the automatic free upgrade. Had to have the laptop repaired and when it came back I had to upgrade again. Made an iso and did that. Laptop needed further repair. When it came back I had to upgrade to w10 again. Problem
now is it won't activate. Both times there were hardware changes.

The laptop was bought with w8.1 preinstalled but I have the original product key. My current w10 is saying I cannot activate as the product key is already in use and it is quoting the w8.1 product key

I spoke with an online customer service person and they said needed to rollback to w8.1 and reinstall w10 again. The product id currently quoted is wrong. So, I restored, the problem remains. In addition, if I wanted to rollback again it's now saying restore
would be to windows 7! Aswell as, not being able to upgrade to free w10 anymore as it's been more than a month.

If I call the customer service/activation phone number and use the w8.1 product id, will that work?

 

Lumia 640 XL built in Korea reverts to original language on upgrade to to W10

I own a Lumia 640 XL built in Korea running W8.1. It came with the language of origin, but I was able, after some problems to find the English setting.

I needed an unlocked phone for use internationally and the dual sim is very useful when I travel. However, when I upgraded to W10 the phone reverted to to the original language and caused so much of a problem that I restored W8.1.

Due to lack of support for W8.1, I have lost some functionality, Skype being the biggest problem. Other programs have become unstable as well.

Is there some way to run the W10 upgrade and force the phone to retain the English setting?

 

An upgrade replaces the system it upgrades. If you do 8>10, then you have no rights to use 8 again, unless within a reasonable time, you choose to remove 10 and return your system to 8. You cannot start with an OS and and upgrade and end up with 2 OSs.

 

Thanks FafHrd for the clarification. Of course, I do not intend to run W8.1 in parallel with W10 forever. Only a couple of months while Im checking out W10. I will eventually abandon either 8.1 or 10. How long will I be allowed to run them in parallel, if at all?

 

Answer is the same as what I gave you here: W8.1/W10 dual use, same product key?