“As we near the one year anniversary of the availability of Windows 10, we’re excited to share that Windows 10 is now running on 300 million active devices around the world” quotes Microsoft’s blog.

Microsoft has confirmed that Windows 10’s free upgrade offer will expire on July 29, 2016.After that, you’ll have to pay $119 (Over NGN 23,800) to upgrade on any computer that hasn’t already made the upgrade.
If you upgraded an OEM (Original Equipment Manufacturer) device to Windows 10 for free, then you can still reinstall Windows 10 on it for the lifetime of the device since that license cannot be legally transferred to any other hardware. If you upgraded a retail version of Windows 7 or 8.1 to Windows 10 then after 29 July 2016 you will be unable to fully move that Windows 10 upgrade to a new device using the Windows 7 or 8.1 retail license.

Any new system operating with retail version of Windows 7 or 8.1 license that you may want to move over to windows 10 after 29 July 2016 will not be eligible for a free upgrade to Windows 10; that means you will have to purchase a Windows 10 retail license to get that system updated to the new operating system. You can still purchase an upgrade license for Windows 10, which will cost less than a full version of the OS, and then use it to upgrade your retail Windows 7 or 8.1 system at that point.

Three point summary of the whole information is:

Read more: http://www.istylmagazine.com/news/technology/why-you-need-to-upgrade-to-windows-10-before-29th-july/