SearchMyFiles - Alternative to the standard Search For Files And Folders module of Windows. Duplicates search is also supported.
SMF – Search my Files - SMF - Search my Files v13 is the fastest duplicate files finder and a multi-dimensional - file searcher, - file copier / mover, - file deleter / eraser, - and
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, ...
DocFetcher - DocFetcher is a portable German/English open source desktop search application.
regexxer - regexxer is a nifty GUI search/replace tool featuring Perl-style regular expressions.
Recoll - Recoll is a desktop full-text search tool. Recoll finds keywords inside documents as well as file names.