grepWin - grepWin is a simple search and replace tool which can use PCRE regular expressions to search for...
dnGREP - dnGrep allows you to search across files with easy-to-read results.
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, ...
The Silver Searcher - A code searching tool similar to ack, with a focus on speed.
FileSeek - FileSeek is an easy-to-use file search app that includes advanced functionality for power users!
DocFetcher - DocFetcher is a portable German/English open source desktop search application.