UPDATE!
You can change almost all your hardware, since latest version, you get the option to save your license digitally...
--- How to Activate Your Windows 10 License After a Hardware Change ---
When reinstalling Windows 10 after a hardware change–especially a motherboard change–be sure to skip the “enter your product key” prompts while installing it.
Microsoft has never actually wanted to explain exactly how the hardware-based Windows activation process works. Just replacing your hard drive or upgrading your graphics card shouldn’t cause a problem. If you’ve just changed a few peripherals, Windows 10 may just automatically activate itself after you clean-install it. But, if you’ve changed the motherboard or just a lot of other components, Windows 10 may see your computer as a new PC and may not automatically activate itself.
Head to Settings > Update & Security > Activation and you’ll see a “Troubleshoot” option if activation failed. Click that option and sign in with the Microsoft account you associated your license with. You’ll be able to tell Windows that you “changed hardware on this device recently” and select your PC from a list of devices associated with your Microsoft account. Microsoft’s documentation now explains exactly how this works.
--- Why You Can’t Just Use a Simple Product Key ---
The free Windows 10 license works very differently from previous Windows licensing systems. These all required a product key. Even modern Windows 8 and 8.1 PCs–and new PCs that come with Windows 10–have a Windows product key embedded in their UEFI firmware. If you buy a new copy of Windows 10–for example, to install it on a PC you’re building yourself–you’ll also have a product key.
In this case, the product key would always serve to activate Windows. But Microsoft hasn’t been handing out Windows 10 product keys to upgraders. There’s no way to find your Windows 10 product key if you’ve upgraded for free–you just don’t have one.
found here: http://www.howtogeek.com/226510/how...10-license-after-changing-your-pc’s-hardware/
You can change almost all your hardware, since latest version, you get the option to save your license digitally...
--- How to Activate Your Windows 10 License After a Hardware Change ---
When reinstalling Windows 10 after a hardware change–especially a motherboard change–be sure to skip the “enter your product key” prompts while installing it.
Microsoft has never actually wanted to explain exactly how the hardware-based Windows activation process works. Just replacing your hard drive or upgrading your graphics card shouldn’t cause a problem. If you’ve just changed a few peripherals, Windows 10 may just automatically activate itself after you clean-install it. But, if you’ve changed the motherboard or just a lot of other components, Windows 10 may see your computer as a new PC and may not automatically activate itself.
Head to Settings > Update & Security > Activation and you’ll see a “Troubleshoot” option if activation failed. Click that option and sign in with the Microsoft account you associated your license with. You’ll be able to tell Windows that you “changed hardware on this device recently” and select your PC from a list of devices associated with your Microsoft account. Microsoft’s documentation now explains exactly how this works.
--- Why You Can’t Just Use a Simple Product Key ---
The free Windows 10 license works very differently from previous Windows licensing systems. These all required a product key. Even modern Windows 8 and 8.1 PCs–and new PCs that come with Windows 10–have a Windows product key embedded in their UEFI firmware. If you buy a new copy of Windows 10–for example, to install it on a PC you’re building yourself–you’ll also have a product key.
In this case, the product key would always serve to activate Windows. But Microsoft hasn’t been handing out Windows 10 product keys to upgraders. There’s no way to find your Windows 10 product key if you’ve upgraded for free–you just don’t have one.
found here: http://www.howtogeek.com/226510/how...10-license-after-changing-your-pc’s-hardware/