DocFetcher - DocFetcher is a portable German/English open source desktop search application.

grep - grep is a command-line utility for searching plain-text data sets for lines matching a regular...

SearchMyFiles - Alternative to the standard Search For Files And Folders module of Windows. Duplicates search is also supported.

PowerGREP - Quickly search through large numbers of files on your PC or network using powerful text patterns to find exactly the information you want. Search and replace with plain text or regular expressions to maintain web sites, source code, reports, ...

Recoll - Recoll is a desktop full-text search tool. Recoll finds keywords inside documents as well as file names.

dnGREP - dnGrep allows you to search across files with easy-to-read results.