I used to use a great plugin for Outlook called "Lookout" that handled the indexing of my email and files (local and network).
It did super fast searches, used very little resources, and was free. It was a Microsoft beta program and was only around for a few years. They got rid of it when they incorporated search into Vista.
The problem with Vista's search (as well as Google desktop search) is that when the file set get large (3+GB email and 100GB's of files) it uses up a ton of resources and slows things down to an unacceptable degree. Neither MS or Google desktop search is all that standout on indexing network files either.
Man, how I miss Lookout!
That why I was so excited to read in TechCrunch about a new indexer (and much more) called Xobni ("inbox" backwards - oh how these email search apps like the backwords spelling!), now in beta and about to be aquired by Microsoft. It looks like a lightning fast indexer, with catogorization, meta data, threaded discussions, and web-lookup thrown in.
Oh, how I want this!!!
I'm hoping to start the beta soon!