Windows can get fragmented
Smart Defrag (totally free, however hit
decline on the toolbar agreement... it's annoying -- 'Nuff said.
EDIT: The last time I mentioned this program, someone asked why in the world I would want to disable Windows' built in self-optimization functions for a third-party solution. To which I reply, the first part of the sentence (Windows' built in
self-optimization functions) is a complete oxymoron.
If you don't believe it, try it. The uninstaller included does work.

If you install the Toolbar on purpose or by accident, just uninstall the "IOBit Toolbar" program, and reset your search settings (they get set to Yahoo! IIRC) and homepage settings.