Earlier last month, Windows Search 4.0 (WS4) was released on the Microsoft Download Center for x86 and x64 flavors of Server 2003, XP, Vista, Server 2008. The update has begun to appear on Windows Update (WU), and companies can begin to deploy it with Windows Server Update Services.

WS4 is marked as "optional" for XP users (you have to visit the WU site to install it) and "recommended" for Vista users (if Automatic Updates are enabled, Vista SP1 users should receive the update automatically). Personally, I did not install it when it was released and I am only doing so now that it is available via Windows Update. Here is a brief list of improvements that WS4 adds over WS3 (the search version that comes with Vista):

It should be noted that the Windows Search team has updated the structure of the search index in WS4, meaning that reindexing of user data is necessary and will occur in the background after installation and reboot. The reindexing process will slow down as soon as it detects mouse or keyboard activity, or when another application requires computer resources.

If you don't see WS4 on Windows Update, don't fret. Microsoft has said it is rolling out the new version gradually during the end of July, and you can still download it manually whenever you want. If you want to stop this update from arriving on your computer, read KB article 953959.