The “Diskmeta”:http://diskmeta.com/ search engine ‘works on all Windows platforms (98 or higher)’ and ‘ is fast, intuitive and unfussy. You can also view the raw text in a special preview window but doesn’t have a preview facility like X1, dtSearch or the new Copernic Desktop Search’. Unlike some other desktop search engines it supports a variety of “boolean operators”:http://diskmeta.com/en/doc/request.asp.
The free version (for non-commercial use) only indexes txt, .doc and .html however – for indexing PDFs you need to pay, and Diskmeta doesn’t index Outlook email.
Thanks to Jeremy Wagstaff for the heads up.
Also see “here”:https://blog.org/archives/cat_search_engines.html#001230 and “here”:https://blog.org/archives/cat_search_engines.html#001202 for earlier coverage of hard disk searching programs.