Desktop search has certainly come a long way. From merely indexing your files and documents, today’s desktop suites are far more capable. They can easily index images, office documents, email, searches, maintain a list of searches, keep a timeline of your PC, and more.
Seeing this list of features, one may conclude that these are paid products. However, this could not be further from the truth. Some of the best desktop suites are free. Not only do they continue to evolve, they get timely updates and are in many ways now essential for a power user. Here's a list of four of the best.
Google search for the desktop. Nothing needs to be said beyond those five words. This application offering from the company that put search on the map is a polished performer that has a huge list of usable features. Apart from your files, it can index your office documents, outlook email, and surfing history.
In its latest incarnation (version 5) Google Desktop is closely integrated with its online services. While this may bother a few people, it's a welcome move as it allows you to pull up documents from across various PCs (at home or work). Tracking that pesky document you wrote a year ago was never easier.
You can download Google Desktop here.
It is the best thing. 
