DnGrep is a powerful text search and replace tool for Windows.
While the program is absolutely packed with features and settings, smart interface design means these won't get in your way. Initially you can just launch it, specify a path to search, a text string to look for, then click Search and wait for the results. (Although even this delivers more than you might expect, as the program can search archives, PDFs and Word documents, as well as plain text files.)
When you need more power, you can tweak your search by setting up custom include or exclude filters. You're able to search only files in a given size range, to include/ exclude hidden and binary files, even to search files of a specific encoding only.
DnGrep supports various search types, including text, regular expressions, phonetic and (for XML documents) XPath, and has options to run case-sensitive, multiline or whole word searches.
By default any search matches are displayed in a Results pane. You're able to move, copy or delete the full set of files, or zoom in on a particular document to open it, browse its containing folder, maybe view its properties.
This doesn't just have to be about searching. If you need to replace your text string as well, enter any new text in the Replace box and dnGrep will modify its matched files accordingly.
Configuring all this can take a little while, at least initially. But dnGrep maintains all your settings between sessions - even the "search for" and "replace" text - which keeps the tweaking to a minimum. It also maintains a history of recent searches, and there's a Bookmark system for queries you'll use regularly.
DnGrep crashed a couple of times during our tests; we don't know why, although running it as an administrator seemed to help. But otherwise the program is an excellent GREP for Windows, stuffed with searching features, but with an excellent interface, and generally very easy to use.