If Java stuff is ok then you might want to check into Jakarta Lucene .

If Java is a no go then under NT 4.0 and IIS 4.0 the "default text search" was to use the Indexing Server. One thing to remember though is Indexing Server/Service is one of those things that seems to usually be comprimised in most virii situations.

Try swish-e. It's as good or better then ht://dig. All you might need is ActiveState's perl, in order to run the sample CGI scripts under IIS. Or, find a c++ binary that will do your searching. Swish-e is 90% libraries and server side indexing, and 10% CGI that just calls the libraries to search the indexes.

I'm no fan of it, but IIS should come with M$ Content Indexer. Use it, clean up the sample asp script to use your site layout and that should be it. It can index office docs and PDF files too.