Better File Select 

Better File Select is a shell extension for the Windows Explorer, which allows users to quickly select multiple files based on a range of criteria. You can use wild cards, partial name matches or regular expressions.
windows explorer shell extension selection selecting wild card regular expression filter filtering

AJC Grep 

AJC Grep is a powerful file finder, text search, replace and data extraction program for Windows. This is a major time saving tool for developers, documenters, web designers and anyone who has to search and replace in a large number of files.
grep find replace search