Altavista Discovery is a product that allows you to index the text on your system. If you burst the archives into separate files (one for each message), it would allow you to access them using their search engine.
You can do queries like "mantis agia claw" to find files that had those three words in them.
I tried a Beta version of this about a year ago and it worked pretty well. I don't know what its current state is, but navigate to " http://discovery.altavista.com" to find out more. It's a free download.
-- Dave Lebling
(aka vizcacha)