Netro Support: Microsoft Windows

For security, please use the latest version of Windows and ensure all the latest software updates are installed.
To protect your data, backup regularly.

Which Windows operating system am I running?
Windows lifecycle fact sheet
Windows 10 upgrade Free upgrade offer expired 31-Dec-17.
Windows Update: FAQ
Windows Support
Windows 10 release information
Wikipedia: Microsoft Windows
Wikipedia: Windows 10 version history

Updated May-18, please report broken links to support.