There was quite the buzz around the office today about the newly released Windows Search 4.  Amongst other things, this release improves the performance and stability over previous versions of Windows Search (read: the search included natively in Windows Vista as well as the add-on to XP).  Moreover, applications that leverage the core windows search infrastructure (such as Outlook and OneNote) should also see a perf benefit as well.

Check it out here: http://support.microsoft.com/Default.aspx?kbid=940157.