Release candidate 1 of this service pack is available in a limited distribution.
You probably don't want to mess with it yet. There's nothing in it so compelling
that you need to install a pre-release set of fixes and minor features.

It is an important service pack, though, because it makes one baseline platform for
the most popular version of Windows, bringing them up to date with the latest fixes
and some new features.

So what is in XP SP3? You can find out in Microsoft's Windows XP Service Pack 3 Overview.
This white paper describes what is and is not in SP3. Some basic features are upgraded,
such as Microsoft Management Console to 3.0 and WPA (WiFi Protected Access) to 2,
but Internet Explorer is not upgraded to version 7.

There are two new features added to Windows with SP3: Black hole router detection,
in which the networking stack tries to determine if routers are silently discarding packets.
Also added is support for NAP (Network Access Protection), which lets network administrators
set policies for system configuration and health, for instance by requiring that specific
updates be installed before a client be allowed to log on to the network.

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