Can I add new retail key to a system already having activated retail key, then use the second one later on a PC?

[Gamer Guy]

I am having a laptop with windows 10 Pro retail key digitally activated and linked to my Microsoft account.

 

I am getting a great deal on Win 10 Pro retail key from a local seller (25 character key) at a great price.

 

But since he has limited quantity available and my PC parts are on the way, I want to buy it now.

 

If I buy now and I want to check whether it is working or not, can I use this newly purchased key with my laptop (key links to the same Microsoft account, because 30 keys can be linked to one MS A/C) and check whether it is working and then after a week or two when I complete my build, I will login with this same Microsoft account and use the second key to activate new PC's Win 10 Pro?

 

Does this work?

[Nayr438]

1 hour ago, Gamer Guy said:

I am getting a great deal on Win 10 Pro retail key from a local seller (25 character key) at a great price.

There is a good chance it's not actually a retail key but rather one bought in bulk not intended for re-sale, in which case the internet is flooded with them.

If your worried about it being a legitimate key, you should buy it from a Authorized seller such as Microsoft, where you will obtain a actual proof of purchase, which is currently $200 USD.