From bleepingcomputer.com
Steam is no longer supported on Windows 7, Windows 8, and Windows 8.1 as of January 1, with the company recommending users upgrade to a newer operating system.
The gaming company warned last year that the Steam client would be unsupported in the New Year, displaying a countdown at the top of the gaming client showing how many days before the game client will no longer receive software updates.
The Steam client now shows 0 days left, linking to a support article about the end of support.