Steam drops Windows 7 and 8 support with the latest client — users told to ‘update to a more recent version of Windows’ to continue gaming
by from Latest from Tom's Hardware on (#6S5WD)
Valve released the latest Steam client version on November 5, which drops support for Windows 7 and 8. Users are advised to "update to a more recent version of Windows" to continue gaming. SteamOS should work as well.