Locate is a free application that is an enhanced Windows equivilent of the Unix locate utility. It allows a quick lookup of filenames on your computer. It automatically updates whenever files are created, deleted, or renamed, without further user intervention. Note that it does not index the contents of files, but only their names.

Download here.

Use is straightforward, by searching for terms through the GUI, located in the System Tray:

Or from the command line: