It had to happen, just a matter of when...
The Register: Google launches desktop search for Windows PCs
Boston Globe: Google search program gets jump on Microsoft
There is an online help file...install is problematic: for me at least: 'not compatible' error - http://desktop.google.com/support/bin/answer.py?answer=10742. I'm getting this issue, so I've yet to know how well it works.
I've been using Lookout, which has worked pretty well for me for a while....requires Microsoft Outlook though.