Windows 7 to 10, with an old key

 I had thought that a windows activation key is valid for any version of Windows. In other words, if I had a Windows 7 version and I extracted the windows key from it and then swapped or attempted a fresh install of Windows 10, I could use the same windows key. But Windows has for sometime now, blocked using windows 7 or 8 key to directly activate new windows 10 installation. 

But there is a way to work around that too. 

Basically the windows key is tied to the motherboard and not the HDD or the SSD. 

The trick is to digitalize the key, from within windows 7 

1. Upgrade from within w7 to w10... here
2. After upgrade, and once on the w10 desktop, connect to the net and go to windows activation (Settings>Security>Activation). This should read as 'W is activated with a digital license'
3. This digitalizes the license and links the license to your motherboard, recognizing your laptop with a genuine w10 license
4. Physically swap your hdd with an ssd
5. Install w10 using your bootable drive and when prompted to feed in the activation key, skip it to say you don't have the key
6. After the w10 installation is done, connect to the net and w10 connects to the net to recognize your laptop has a digital key on your motherboard and activates the key

Basically, learnt that the key is linked mostly to the motherboard rather than the ssd. 

PS: The key is hardwired to the system!  One cannot use a key on another system, unless the key is bought separately and did not come pre-installed with the system.