Vista 64. An external drive is always assigned K and search always returns "no results." If change drive letter, search works OK. This seems to be recent.
Plug in the drive (getting K to appear and be available) and then make sure K is included in indexed locations and then rebuild the search index: http://www.vistax64.com/tutorials/69581-indexing-options.html. I believe this will take care of the problem.