According to unofficial reports, Microsoft will ship XP Service Pack 3 to OEMs and MSDN subscribers on April 21st. The service pack will then become available to the general user population through Windows Update service beginning April 29. Microsoft has remained mum on the official release dates only stating it expects to release the update in the first half of this year. You can expect a pretty hefty download as it includes all updates since the release of SP2 back in 2004 as well as additional enhancements including Network Access Protection that attempts to ensure a computer has a clean bill of health before allowing it access to a network. Other features include detect routers that are dropping packets and allowing setup a la Vista where the product keys don't need to be entered during installation.