Microsoft decides Vista SP1 x64 is ready for release
Despite expectations for a March 18 release, reports all over the Internet have surfaced that SP1 x64 RTM has been released via Windows Update. Not everyone seems to have access to it (yet, keep hitting that “Check for Updates” button): it has only appeared for certain individuals at the moment. The update is of course optional; users need to manually choose to download it even if they have their Windows Update set to retrieve updates automatically.
Read more: arstechnica.com