I just wanted to use the Windows search function in order to find “a word or phrase in the file”. No chance! It has now happened to me several times that no files were listed at all, although I knew that my search expression was inside one of the files. Today I finally started searching for a solution and was surprised to find it directly at Microsoft.

Here’s the brief version:

1. Right click “My Computer” → “Manage”
2. Fold out “Services and Applications”
3. Right click “Indexing Service on Local Machine” → “Properties”
4. On the “Generation” tab activate “Index files with unknown extensions”

That’s it!

(Background: For no obvious reason, Windows XP only searches those files by default, whose extension has been registered as a file type – e. g. by some application. All file types Windows does not know are simply being ignored by the phrase search.)