Search for [Menu]

How do I perform the above search from windows explorer on Windows 7? I want to search within files also. I tried Content:=[Menu], but this gives me results including the word Menu without brackets. I tried enclosing it in quotes also, but that still doesn't include the brackets. I only want results (file names) that include the term [Menu] inside the file.

Thanks

I think I answered my own question, sort of. This time when I tried, I found no results instead of too many. I believe the search is working, but all the files are not .txt files. How can I make the search work in non-text files? They really are text files, but the extension is not always txt.