1)   Halftone Search for Google Desktop 1.2.6
This program extends the Google Desktop (GD) and Windows Search functionality by providing a native Windows interface and allowing GD to access more file formats. Allows you to customize the look and feel, manage plugins, handy search and more...

 2)   Instant Document Search 1.12
Very fast document search engine for your computer or local network. Support of MS Office files, WordPerfect, PDF, web pages, plain text files and other documents. Instant Document Search is easy to use, but powerful tool.

 3)   XSearch 0.1
XSearch is a free search tool that with more features that Windows Search didn't provided. It can search files on your computer in high speed. When searching for special words in files, you can specify the words option etc.