Desktop search tools search within a user's own computer files as opposed to searching the Internet. These tools are designed to find information on the user's PC, including web browser history, e-mail archives, text documents, sound files, images, and video. A variety of desktop search programs are now available; see this list for examples. Most desktop search programs are standalone applications. Desktop search products are software alternatives to the search software included in the operating system, helping users sift through desktop files, emails, attachments, and more.
Lookeen desktop search on Windows
Windows Search is a content index and desktop search platform by Microsoft introduced in Windows Vista as a replacement for the previous Indexing Service of Windows 2000, Windows XP, and Windows Server 2003, designed to facilitate local and remote queries for files and non-file items in the Windows Shell and in compatible applications. It was developed after the postponement of WinFS and introduced to Windows several benefits of that platform.
A screenshot of Windows Live Search Center