Heres a method posted on Search inside files does not work
by a user called CTN222.
"Using windows explorer; from the left side select the folder you want to search.
Then in the upper right hand corner (search box) enter what you would like to search for, lets say "test"
At first windows will search for all files that have "test" as part of the file name, but if you
SCROLL to the bottom of the search results you can see the following:
Search again in:
Libraries / Computer / Custom / Internet / File Contents
Click on File Contents and it will perform a search within the files for the keyword "test"."