Google Desktop is the latest thing out of googles beta program, predictably it puts Microsofts Windows searching capabilities in the shade. It’s a small (~400k) download.
It operates in a similar fashion to Microsofts search in that it builds up an index and then searches that index. Unlike Microsofts tool, it builds up the index only when your computer is idle. This means there’s a speed improvement over Microsofts search, however it does mean that it can take a while to create the inital index.
The search is accessed using an icon in your system tray, this then launches your web browser and takes you to the familiar google search page, the results are listed in pretty much the usual way, except you can choose to view only files, only web history, only IM conversations or only emails. The desktop search is also integrated in the web search, so if you have something relevant to your web search on your hard drive, google alerts you.
There are a couple of downsides though - at the minute at least, Microsofts search more items, MSN Messenger chat logs is one thing I’ve noticed, and I think ID3 tags. However google are planning on making more items searchable. Once it includes chat logs for different clients, and reads exif information and id3 tags, I believe it will be far more useful. The other downside is that the Microsoft search is more integrated, I believe that google should replace the Microsoft search that appears when you press Search in Windows Explorer, I assume that it is possible as it can be changed in Internet Explorer.