Gary has been looking for an alternative for desktop search. Leo says that X1 is his favorite, but you have to pay for it. It starts searching as you type, which makes it really fast. It searches into emails, documents, and everything using keywords. Copernic is still around as well, but it's dated. X1 is modern and up to date. It's the king of the hill.
The chatroom recommends Everything Search Engine by VoidTools, and it's free. It doesn't look into documents like X1 does, though. Jam software's UltraSearch and Mythic Software's Agent Ransack are other options.