Index file contents of unknown file type

Question

I would like to index the file contents of unknown file types. This window allows you to change settings for a particular file type, but I want to avoid doing that with each file type I have that is not known to Windows.

I have used the registry key

HKEY_CLASSES_ROOT\Unknown

before but I do not see how to use it in this situation.

Answer 1

When someone else asked this question, the response from a Microsoft MVP was to use a third-party program. Apparently even Microsoft acknowledges that the search function in Windows Vista+ is useless.

Windows uses two different registry entries for file-types. There is an entry for the actual extension which in turn, points to a corresponding file-type entry.

For example, text-files will have an entry at hkcr\.txt which will contain a reference to txtfile that points to hkcr\txtfile which has type-specific information. (Multiple extensions can point to the same type; e.g., .cpp or .mytype can point to txtfile to have them treated like text files).

If you use a registry-activity monitor (e.g., with Process Monitor), you can watch the Indexer enumerate and access HKCR’s sub-keys. Unfortunately the Indexer does not access the type-specific entries which is what unknown is. It only enumerates extensions, and since unknown types have no extension (well they do, but they vary), there is no way to manually register unknown types with the indexer.

That said, indexing unknown types was doable in Windows XP (figure 1). You can try using the same option in Windows 7:

1. Open the registry-editor

2. Navigate to the following registry key:

   HKLM\System\CurrentControlSet\Control\ContentIndex\FilterFilesWithUnknownExtensions
   

3. Locate the DWORD value FilterFilesWithUnknownExtensions or create one if none exists
4. Assign it a value of 1 to index unknown types or 0 to turn off unknown type indexing
5. Restart the Windows Search service

If that still doesn’t work, then I’m afraid the ability to index the contents of unknown files has simply been removed from the indexer in Vista and up.

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Figure 1: Windows XP’s unknown-type indexing option

Answer 2

The free and popular Notepad++ has a useful feature to search file content within a directory, recursively. I use it often. Scans all text files, including unknown file types.

Additional feature: well integrated with Notepad++. The entire matching line is show in search result, with the target phrase highlighted. Click any line to open the file in Notepad++.

It treats binary file content as a bunch of funny characters.

It takes time when searching big files, but it doesn't crash.

This solution doesn't use indexing, but solves the problem nevertheless.