Ran into the same problem after upgrade from Windows 8.1 Pro. Since there is no official method to reset Indexing Options to the defaults, I just removed the corresponding registry branch. After the whole procedure, Windows restored the branch in its pristine state and the indexing resumed to work properly.
STEPS TO PERFORM:
Stop Windows Search service:
Win + R, services.msc
, Enter
Find the Windows Search entry, click on it, and choose Stop from the left column.
Remove the following registry branch in its entirety:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Search\CrawlScopeManager\Windows\SystemIndex
You can use the free home edition of Registrar Registry Manager for this.
Follow the step #1, but click Start instead of Stop this time.
The service will start and re-create the missing registry branch. This action will effectively set the Indexing Options to their clean default state.
The Control Panel (or Settings) items are now shown in the search results, immediately, but if you feel like to, you can set your own exclusions via the usual Indexing Options interface and even rebuild the index.