The desktop search for Windows Vista has been updated with faster indexing and faster query response times. In addition, the search index continues to build indices after a system failure. Windows Search 4.0 also works with Windows Server 2008, Windows XP, Windows Server 2003, and Windows Home Server.
Windows Search 4.0 lets you perform an instant search of your computer. Windows Search 4.0 helps you find and preview documents, e-mail messages, music files, photos, and other items on the computer. As ISVs can add search results to your application onto Search results. To learn more, see Windows Search 4.0 for Developers. There you'll find samples.
According to a post on MSDN Forums, "The search platform is unchanged between WDS [Windows Desktop Search] 3.01 and WS4 [Windows Search 4.0]. We did not ship a separate SDK for WS4 because the Windows Search SDK is now integrated with the Windows Vista SP1 SDK which can be found here." And that means you can get started adding your own search results just as you could do in previous version.
Windows Search 4.0 is available from Description of Windows Search 4.0 and the Multilingual User Interface Pack for Windows Search 4.0.
The search engine in Windows Search 4.0 is a Microsoft Windows service that is also used by programs such as Microsoft Office Outlook 2007 and Microsoft Office OneNote 2007. A feature called remote index discovery allows user to search files across different Windows platforms. IT Pros have more control over searches in Exchange server, file shares, and certain encrypted files. If the client is running Windows XP or Windows Vista, the search UI can send queries to an organization's search servers anto combine results.