If you are seeking a desktop search tool which grants you, the user, complete
control, and which stores your data ONLY on your local PC, not communicating
anything to any outside source, then give Copernic Desktop Search a try.
It's 100% free for non-commercial home use. The web site is
http://www.copernic.com/en/products/desktop-search/ . You can set CPU
priority and control how indexing is done and where the index is maintained.
Impact on the system is minimal.