The only problem is that sometimes, you may still encounter activation errors, which you may not resolve until you contact Microsoft support directly and explain the situation. Generally speaking, you do not have a limit on the number of times you can transfer a license as long as you deactivate the previous installation, so you're not using the same product key on more than one system.

If you plan to upgrade to Windows 10 from Windows 8.1 or Windows 7 with a retail copy, you can also move the product key to another device. If you purchased a Retail license of Windows 10, you are entitled to transfer the product key to another computer. Microsoft uses different channels to distribute Windows 10 licenses, but consumers can only obtain a license through two channels, including Retail and Original Equipment Manufacturer (OEM). How to determine whether you can transfer a product key on Windows 10

How to transfer a product key to a new PC on Windows 10.

How to determine whether you can transfer a product key on Windows 10.

In this Windows 10 guide, we'll walk you through the steps to transfer a product license key to a new computer.

Device doctor pro license keys list