Upgrade W10 Edition with W7 key, possible?

Go to activation menu - click on link "go to store".

This takes you to pro purchase menu.

Under the buy pro 10 button is a link "I have a Pro 10 key".

Click on that and enter 7 Pro key.

See if this link helps https://support.microsoft.com/en-us/...0-why-activate

Or you could try this

1. Press “Windows key + R” to get the run window.
   
2. Type “slui 4” and press enter.
   
3. Select your 'Country' from the list.
   
4. Choose the 'Phone Activation' option.
   
5. Stay on the phone (do not select/press any options) and wait for a person to help you with activation.
   
6. Explain your problem clearly to the support person.
   
7. Follow the on screen directions to activate over phone.

essenbe said:

See if this link helps https://support.microsoft.com/en-us/...0-why-activate

Or you could try this

1. Press “Windows key + R” to get the run window.
2. Type “slui 4” and press enter.
3. Select your 'Country' from the list.
4. Choose the 'Phone Activation' option.
5. Stay on the phone (do not select/press any options) and wait for a person to help you with activation.
6. Explain your problem clearly to the support person.
7. Follow the on screen directions to activate over phone.

Read OP post again.

The issue is not activation.

The issue is he is trying to upgrade to PRO from Home!

Ren said:

OK, that's good idea, I will try phone activation. So basically, what I am trying to achieve should work, right?

No 100% - it will not work. You have to upgrade to Pro.

What version of 10 home do you have installed 10240 or 10586 (run winver).

You need to upgrade to 10586 to use 7 key.

In answer to other post, the change product key option is not same as clicking on the link I told you about.

Yes, I do have 1511 (10586) patch installed.
edit:\>

So, this is how it looks after clicking the link 'I have a W10 Pro key.' and I'm still confused. Should it work or not?

edit2:\> Well, I called the activation line to ask if my key is alright but there's only a machine, which goes directly to entering first block of installation ID which I do not have, obviously. No option to speak with live person.:-( I even tried another (last) W7Pro key I have available, no luck, same thing.

To update Win 10 Home to Pro you need a Win 10 Pro key (even the generic)

To activate Win 10 Pro a Win 7 COA key can be used (I assume it's from the same PC being updated?
(...otherwise it's contrary to the EULA, and NavyLCDR will send the Marines to your house and confiscate your PC's)