If you need to make a fresh Windows installation then you'll most likely need your Windows product key to activate it.
The good thing is that there are numerous ways to find out your product key. Let's take a look at them.
Method 1 - Use the Command Prompt
You can easily find your product key by using the command prompt. To open your command prompt, go to your Windows search bar and type CMD.
All you have to do is copy and paste this command "wmic path softwarelicensingservice get OA3xOriginalProductKey" to your command prompt. Execute it and you should be good to go.
However, as you can see above, that method didn't work out for me. I imagine that this happened because I've got a digital license.
If you also have a digital license, then you don't need to insert a product key. Windows will recognize your computer and will eventually get activated automatically after you sign in to your MS account.
Digital licenses are mostly found in computers that used the free upgrade from Windows 7/8 to Windows 10.
Method 2 - Find Product Key in Registry
The product can also be found at the registry, but you won't be able to read it as it is. Here's it's location:
Your product key is "DigitalProductld" and as mentioned above, it doesn't make any sense in its current form. You need to "translate" it by using 3rd party programs/product key finders.
Method 3 - Use 3rd Party Software
This is quite possibly the easiest, fastest, and most effective way of finding your key. There are numerous programs that can do this job for you - both free and paid.
Free product key finders often work just fine as well - it's just almost all of them display ads which is something that you would expect.
Method 4 - Look at your Case / Disc
If your computer had Windows pre-installed or if you got it on a physical disc, then chances are that you can find your product key printed there.
In case that you've got a Laptop, look at the bottom cover of it or under the battery if it's removable.
My Laptop which came with Windows 7 pre-installed has its product key printed right under the removable battery.
That's useful in case that you need to find your product key after you've already wiped your previous Windows installation.