AstroGrep is a lightweight Open Source user-defined file search utility.

AstroGrep is a portable tool and does offer a bit more flexibility in searching than the default Windows search - it includes useful features such as regular expressions, adaptable printing options, stores most recent used paths and has a "context" feature for easily viewing source codes.

AStroGrep Features:

Regular expressions
Concurrent multiple file types
Recursive directory searching
A "context" feature that selects the lines above and below your search expression
Versatile exporting and printing options
Right click to open file with editor of your choice at specific line (if setup)
Store Most Recently Used file names, file types, and search expressions
Match Whole Word Only
File encoding detection (ability to turn off and override for individual files)