Search for words in a file

Here, as refers to A. As file (that is, an ActionScript file, which is a text file), but the method provided here is generic, that is, you can search for words in any text.
We know that "one word or phrase in a search file" in the default search function of Windows is only valid for some file types.
The method I first came up with was to rename a class library folder traversal. As->. txt, and then change it back to. txt->. As. The method used is the for command in cmd, for example:
For/r f: \ papervision \ as3 \ trunk \ SRC % F in (*. As) Do Ren % F % ~ Nf.txt
Where "F: \ papervision \ as3 \ trunk \ SRC" is the specified directory, modify it by yourself, and restore:
For/r f: \ papervision \ as3 \ trunk \ SRC % F in (*. txt) Do Ren % F % ~ NF.
Valid, but troublesome.

Then find the official Microsoft method (reference http://support.microsoft.com/kb/309173/zh-cn), modify the Registry (Regedit), find
HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Control \ contentindex
The filterfileswithunknownextensions value is changed to 1.
In this way, you can find words in any type of text files. It should be a practical technique.