I have not had a chance to play with this, as it is limited to Windows/IE, but that's OK, Danny has, and his very thorough write up is here. What I'm interested in is what this all means for the big Chess Game That Is Search, and frankly, this is A Very Big Move on the part of Google.

Recall, if you will, about a year ago, when Google launched the Deskbar, which integrated into IE and allowed for search from within that environment. Recall further the rumours of a desktop search tool (back in May, broken by Markoff at the Times.) All of this fed understandable speculation about a Google browser. Well, the other shoe is dropping this morning. It's not a browser, but it is a significant desktop client application: Google Desktop Search. With this launch, Google is focusing on placing a desktop application on your computer that *makes your browser seem smarter.* The browser (IE only for now) becomes the interface front end to a major Google incursion into the PC hard drive, a space that heretofore has been owned by Microsoft. Google isn't competing with Microsoft on the browser front - that would be madness. It's competing with Microsoft on its own terms and its own turf: by integrating the desktop into the web browsing experience. More specifically, but integrating it *into the Google experience* as understood through search.

This is the part that's important: As far as the user is concerned, Google's Desktop Search seamlessly integrates your hard drive into Google.com. "Desktop" becomes another tab, right next to "Web", "Images", and the like (your data stays on your hard drive, of course, but to most mere mortals, it might seem like in fact it lives "out there on the web.")

Yes, this is a Big Deal. For many reasons. Assuming you download the client and use Google Desktop Search:

One, it means Google will have a major beachhead on users' computers - an index of *everything on your hard drive.* Yes, this raises privacy concerns, but Google has outlined their stance on this in the documentation, and (compared to Gmail) seems ready to handle this issue this time.

Two, it means that index will be viewed *in the native Google interface* - for all intents and purposes, it treats your hard drive as an extension of the web (or, vice versa...it hardly matters which). MS Word, Powerpoint, Excel files? Just results in the Google interface. How's that for a lightweight OS?***

Three, it means that Google can build upon that knowledge of your personal data to make *all* search more relevant for you - this is Google's first major foray into truly personalized search.

Four, it means that everything is now searchable: your email, your Word documents, your music, your IM sessions, and - pay attention here - your SEARCH HISTORY. That's right, the Google Desktop Search automatically hoovers out *every site you visit* from the IE logs and adds it to you overall searchable index as cached pages. "Take that, A9, Yahoo, and Ask," Google is saying. "We're playing here too...Oh, and by the way....we're Google."

And Five, this provides Google a major new platform to build upon - a client application that integrates with the web. Can I imagine upgrades to that app that include spiffy new features like - oh - a lightweight word processor so you can take notes on your searching, or a calendar? Better yet, can I imagine Google opens this platform up to third party developers, to do what they do best? Yes, I sure can.

As I intonated before, Google is playing to its strengths, leveraging its power as the defacto interface for finding things on the web over to the desktop. Once it begins to know more about you (recall that John Doerr hinted at this just last week at Web 2.0, saying "Google will become the Google that knows you"), expect a hell of a lot more innovation from Google on this front. Yup, that means, eventually, lessons learned from millions upon millions of aggregated individuals' search histories (and desktop usage patterns) will start to inform Google's overall approach to relevancy. How could it be otherwise?

I reached Google's director of consumer web products Marissa Mayer at 9 pm last night as she was catching a red eye to New York, where Google is announcing Desktop Search at the Digital Life conference (a consumer-focused event starting today). Marissa is known as a superwoman at Google, she works constantly, and only travels on the red eye so she won't miss a business day. (Yikes....I remember those days...).

After she caught her breath, I asked her these questions:

- Why did you develop this product? Did this bubble out of the labs like News, or was it more deliberate?
We view this as an important development and it's just the start of many new innovations. Our users have been asking us for this feature from us for five years. We started working on it about a year ago. Steve Lawrence is the lead researcher. (So no, it was not a Labs project).

- Was this a response to all the other competitive announcements in personal and desktop search?
No. The technical details of this product are stunning. It only uses of 8 megs of RAM to run. It's a 400 Kbyte file! Our first build was in February, and we had a lot of testing and revision. We targeted launch for October because we are sponsoring Digital Life and this is perfect product for that conference.

- Do you think this will quell all the Google browser rumors?
We were trying to fulfill a user need. In 1995 the browser model worked fine - you could find what you were looking for by browsing a directory like Yahoo. But over time as the web scaled that model didn't scale. It broke, which is why search (became the metaphor for finding things on the web). We are seeing the same thing happening now on personal computers (which have far more storage than even five years ago). The distinction between the hard drive and the net is becoming blurred. We want this application to be a sort of photographic memory for your screen. (She ducked this question...but then again, she was running to catch a plane...)

- How does the Google Desktop Search do ranking on a person's hard drive?
The default rank is by date. (When we tested, we learned that) people understood the context of "when they did see this"? The results list the last time you accessed any particular document. However you can also sort by relevance. The desktop relevance scheme lacks Pagerank (of course), but it does incorporate the other 150 factors (Google uses on the web) - factors like are the (keywords) together, in bold, related, things like that.

- How will you incorporate what you learn from this into overall relevance drivers for Google?
As we see the distinction between the hard drive and the net blur, people don't want to have to choose between the desktop and the web. You can issue your regular search and to the extent there is relevant information on your desktop, we'll write it to the browser. (Again, she didn't really answer that one...)

Net net: This is a major initiative for Google (they ain't rolling this one out quietly through Labs!), and it will be very, very important to the company that this be widely adopted by millions and millions of users (privately, Google employees have told me they were disappointed with the number of their Toolbar downloads over the years). If it is, it will set the stage for a very Web 2.0 battle for the hearts and minds of searching consumers - and that means all consumers - everywhere. In the end, if search becomes the interface for how we navigate our computing space, regardless of where that space is, there is no doubt the power of Microsoft will be diminished. On the other hand, there is no way Microsoft, which bought a desktop search company earlier this year, or Yahoo for that matter, will stand still. This move, I sense, is the true starting gun of a major race to win in search, and at the interface level for all of computing. It should be a fun few years!

PS - Let's not forget that Google laid down policy on desktop applications a while back. This is worth re-reading in light of this announcement...

***- On the OS/Interface stuff, recall what I wrote back in April, after going to MSFT for the day: On the platform idea (point three), my general thesis is this: Over time, more and more of a typical user's desktop real estate is devoted to web-enabled apps. I am an extreme example of this trend (and I'd wager the same is true of most of Searchblog's readers): at any give moment, I've got ecto (a blogging tool), NetNewsWire (RSS reader), Firefox and/or Safari (browser), mail, and Office open. All these applications are web-enabled (Office is the lamest of the bunch, but not for long). Even OSX makes web calls - if only for software updates for now. So if you look at my screen, at least 80 percent of it is web applications. Compare that with five years ago, where it was just email and the browser, or ten, where it was just email.

Now, all these applications are migrating to the portals, and the portals are migrating to the model Cole described: software-based platforms replete with tools and applications - mail, calendar, blogging, rss readers, the works. At some point (and this certainly is not a new idea) the very idea of the "desktop" will become pretty old school. We're building an entirely new architecture on top of our OSes. So...what does that mean for the traditional OS? In essence, it loses the glory role, in the eyes of the consumer. The OS does the hard stuff - files systems, security, connectivity, etc., but the interface, the stuff the user sees, is migrating to the web.

UPDATE: Even though an ad for the Google Desktop appears when you search for the term, so far the site is still not up. Stay tuned.

UPDATE 2: An astute source of mine who works for one of the other Big Portal companies points out that while Google's announcement is a big deal, companies that allow folks to search across their data on servers and services - ie MyYahoo, Amazon, social networks (or implied ones), etc. - may have a leg up in the long run.