Dear Windows Update v5 Beta testers:
The Windows Update (WU) v5 RTM release is coming. As we approach the end of the WU v5 preview program, the WU v5 Beta team would like to thank all of you for helping us make major improvements to the WU site and Automatic Updates (AU). We are expecting a successful rollout of WU v5 and Windows XP SP2. Without the help of the beta testing community and our MVPs that would not be possible.
During the WU v5 RTM site rollout only Windows XP (RTM, SP1, or SP2) will be supported by the WU v5 site. Anyone using Windows 2000 SP3 (or later) or Windows Server 2003 to access the WU v5 site will be redirected to the WU v4 site. We recommend that beta testers with these operating systems re-image their computers to a pre-WU v5 image to return to the state most compatible with WU v4 and AU.
News source: BetaPlace