Since its introduction, Microsoft’s Windows 10 operating system has been a free upgrade for users of Windows 7 or Windows 8.1. The hammer’s about to fall on the free ride, though: after tomorrow, the OS will cost $149 (it will remain a free upgrade for many Windows Phones).
Even if you’re not sure if you want to step up to Windows 10, it’s worth downloading it before the free offer expires; you can perform an upgrade, which will license your PC for the OS, then roll back to your previous operating system. That PC will then be upgradeable to Windows 10 for free at any time, as long as its hardware configuration remains substantially the same.
Asssuming you haven’t done so already: