Replacements for AltaVista Discovery?

Daniel Ashton asks: "AltaVista Discovery was a wonderful tool for indexing files on one's own hard drive. I have most of O'Reilly's CD Bookshelves copied to my hard drive, along with other documentation in HTML or PDF format, and AltaVista Discovery indexes it all. Finding information on Perl syntax or Unix utilities or Java APIs is as easy as entering the keywords in Discovery's search toolbar. A web browser opens with a list of hits and summaries. Unfortunately, Discovery was both 1) single-platform and 2) discontinued. As I anticipate installing a new OS on my machine, I dread loosing this functionality. What alternatives exist? Are such tools available for Linux? For Win2K? Is there a file-format-reading toolkit that could be used to write a new indexer?"