I believe that BEST alternative for default Windows Search is Search Everything.

Search Everything has many merits:-
♥ Smallest Installation File
♥ Low Memory Footprint !
♥ Best response time !
♥ One of the simplest user interface
♥ Quick Look-up
♥ One can use it's server to access and search remote computer !
♥ That too with an added security !

Here is the tool : Everything Search Engine

Guys If you have any other alternative available , Let me know , I am open to test an compare e tool you prefer !