Unclear what you downloaded (a new update from a web distributor which was cheaper than the full version from Microsoft).
Now download the official version (use the "install to another PC" option) from https://www.microsoft.com/en-us/software-download/windows10 (assuming you want the US version), and make a bootable USB-stick or DVD. That's free for everybody.
If your previous version of Windows was legitimate, you don't need a license code to install this one, because Microsoft knows that your PC has a valid one already. If it was some hacked version, you'll have to buy the license key indeed.
I initially downloaded a new windows 10 update from a web distributor on getting the windows installed. I started experiencing some app crashing bug. I also got most of my files corrupted (my really important .txt files). Some few weeks later I tried booting my laptop it too about 3hrs to bootup to the user interface. When I typed the command Ctrl+alt +delete I found out that all my users where being erased and I only got two users , which were (admin user and the guest) does this mean my initially installed os (windows 10) is currupt or I downloaded the wrong file from the wrong source. I also tried the Microsoft main website but I was asked the make a purchase of windows then. The cost was quite expensive that was why I went for the cheaper one. Someone say something am damn frustrated. Need help suggestions.