Recently noticed during MS update that an optional Windows Search 4 was available. I, of course, looked at WW first to see what the buzz might be. Didn't find much. Did a little research, found that it is an actual (optional) upgrade to the Windows operating system, does not phone home, and is free (to validated Win systems).
Creates an index of drive and mapped network drives, based on either group policy or network permissions. Updates on the fly (after index is created). Provides a desktop (task bar) search box. Is VERY quick and provides a preview of found files. Index size is approximately 10% of the content. Can be less if you turn off some functions (indexing content of text files for example). Index is obfuscated and can be encrypted via Bit Locker if desired.
Only con is the time it takes to index the available resources... my system has over 1,000,000 files and I have some external drives I move on and off... will index those as well. Remote sources need to have Windows Search installed and index created to be useful over the network. Can index on-line sources. Can index MS OFFICE docs etc, including Outlook emails. Indexer will back off while using the computer with NO slowdown for the user... but really kills the indexer to a crawl. Regains speed when detects system idle.
For XP SP2 and up (separate version for XP64), Vista, Server 2008.
This is a significant upgrade in capability of the built in search function for XP users. Vista already has a similar indexed search, though this is an upgrade for them as well.
So... if you have a lot of files, a lot of emails, docs, html, etc (over 200 file types are automatically indexed, other types can be added) you might find this useful.
Does allow administrator set up across networks, group policy, all the bells and whistles.
Essential? No. Useful? For me it is.