I have used a bunch of tools over the years to try to search within files, folder and drives, but have yet to find something that works everywhere and in every case.
Lately, I have been using the Windows search tool (the one that comes default with the OS) with some success. So if you are on a Windows Platform, create an import.reg file with the following in it (where .phps is replaced with the extension of files you would like to search inside, such as .cfm .php or .xml). Multiple ones can be added by making copies of the registry key and replacing the extension.
Windows Registry Editor Version 5.00
Save, double click, say yes, reboot and voila, now it searches inside those files for you.
One little tip, try to edit with the default Windows editor or Notepad to get the best results.