According to NeoSmart Technologies Blog (->google cache), which is among those who have received the first version of Windows XP SP3 build 3205 as part of the Windows Server 2008/Windows Vista SP1 beta program, SP3 has more than 1,073 patches/hotfixes including security updates. Among these are a few things that have been backported from Vista including the new Windows Product Activation model, Network Access Protection modules and policies. There is also the new Kernel Mode Cryptographic Module so that the kernel now includes an entire module has access to multiple cryptographic algorithms and is available for use in kernel-mode drivers and services. It also has the " Black Hole Router" detection so that Windows XP SP3 can detect and protect against rogue routers that are discarding data. Looks like XP is becoming a much better alternative to Vista, again. (thanks TheInquirer)