Windows 10 is currently being offered as a free upgrade to users of Windows 7 and 8.1.
However, this is not a mandatory update.
Windows users can stop their machines from going ahead with it.
Depending upon your Windows Update controls, this may cause the upgrade process to automatically initiate on your rig.
And of course, if you choose to upgrade (our recommendation!
Also read:Here is how to stop your Windows 7/8.1 PC from automatically upgrading to Windows 10
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source: www.techworm.net