Finder find problem

I'm a very long-term user, so I shouldn't have this problem. I was cleaning out some programs in the Activity Monitor, so I possibly did this to myself. Now, when I want to find <anything> at all using Finder Command-F, I get a 'searching "This Mac"' window that looks perfectly normal, except that there is no field in which to type in the name info for the file I want to find. And that makes the Command-F useless!

I did learn how to use Spotlight search, but it finds too many unrelated things.

What processes (which should show up in Activity Monitor) are used by the Finder to find files generally, and what processes are responsible for providing a field to type into to identify the intended file (and - perhaps - what processes are needed to display this info). I would prefer NOT having to reinstall OS X.