It only shows what it finds, and it only searches what is already indexed. If you want something to show up, you need to include it in the search indexing, run

It only shows what it finds, and it only searches what is already indexed. If you want something to show up, you need to include it in the search indexing, run a reindex, and wait for the index to be completed (and potentially reboot). For more info, Google "Windows search index".