they are ending Steam client support for Windows XP and
Windows Vista as of January 1, 2019 (thanks
). They say some Steam functionality will be limited between
now and then for those versions of Windows, and as of the new year the client
will cease functioning altogether for XP and Vista:
Starting on January 1
2019, Steam will officially stop supporting the Windows XP and Windows Vista
operating systems. This means that after that date the Steam Client will no
longer run on those versions of Windows. In order to continue running Steam and
any games or other products purchased through Steam, users will need to update
to a more recent version of Windows.
The newest features in Steam rely on an embedded version of Google Chrome, which
no longer functions on older versions of Windows. In addition, future versions
of Steam will require Windows feature and security updates only present in
Windows 7 and above.
For the remainder of 2018 Steam will continue to run and to launch games on
Windows XP and Windows Vista, but other functionality in Steam will be somewhat
limited. For example, new features such as
the new Steam Chat will not be available. We encourage all users on these
operating systems to upgrade to newer versions of Windows in order to have
ongoing access to the latest features of Steam, and to ensure future access to
all games and other Steam content.