Windows Live ships two updates:
1. Update for Windows Live Mail (KB 944990)
2. Update for Windows Live Writer (KB 944990)
These updates will apply to all Windows Live Mail Beta and Windows Live Writer Beta users. The RTM version of this software fixes critical issues, performance issues, and bugs in the beta software. It is recommended that all beta users move to the released version of the software.
All WSUS admins are recommended to approve the update so that managed machines can move from beta to the more stable and secure released versions of the Mail and Writer software. These updates will only update machines with the beta versions installed (Writer and Mail).
See KB article for more details - http://support.microsoft.com/kb/944990Windows Live, WLW, Windows Live Writer, Window Live Mail, Beta, Security Update, WSUS, Windows Update, Microsoft Update, RTM