Using Windows Desktop Search to search for text in files with another extension than "txt"

I use Windows Search quite often on my notebook to look for a file, E-Mail or a program. In Windows you just hit the Windows Key and start typing, which is very convenient.
If you want to start a program you just start typing the program name and hit enter Excel, hit the key and type “exc” and enter, and off you go.
The normal search (files or text within files) is also very powerful. Here is a site which explains the syntax: http://msdn.microsoft.com/en-us/library/aa965711(v=vs.85).aspx and here is a good article http://www.howtogeek.com/73065/learn-the-advanced-search-operators-in-windows-7/ on how to use it.
 
One problem with
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