On the face of it, the answer is simple: Google Chrome is an open-source web browser and, as such, will be aiming to blow Mozilla Firefox out of the water and then train its guns on Internet Explorer.

Indeed as an open-source web browser, you'd think that Firefox is the premier target. And Google Chrome (which will use the same rendering engine as Safari and right now is Windows only) launches only days after Microsoft's major beta release of Internet Explorer 8.0. Game on.

See also: Microsoft slaps Google with IE8: the 'porn browser'

See also: Google Chrome review

But first impressions are not correct, at least not on this occasion.

Mozilla announced today that it had reached agreement with Google to continue its lucrative revenue-sharing deal for a further three years. Firefox makes almost all its revenue through Google, which pays Mozilla for every web search that takes place through the browser's searchbar and default home page.

Each search is an opportunity for Google to display contextual ads, and Mozilla receives a tiny slice of the profit generated. With 20 percent of the web-browser market, those tiny slices soon add up to a healthy great pie. A pie made of cash.

It seems strange that Google would agree to another three years of this mutually beneficial deal, and then launch a Firefox rival. If it wants all of the money, why let Firefox have any? If not, why enter the crowded web-browser market?

And what's with the timing - straight after signing on with Mozilla? Leaked or not, Google knew that Chrome was coming soon.

Over the past few years Mozilla and Google have made very cosy bedfellows. Firefox and Google's various tools play very nicely together, and the companies share common goals. And a common enemy: Microsoft.

Perhaps Google is aiming not for Firefox or even the market leader IE, but for an altogether juicier, and more vulnerable target. Windows Vista.

Regardless of its burgeoning market share, Vista is taking a hell of a beating right now. But if you intend to buy a new PC in the next couple of years, you're not a Mac fan and you don't want to run Linux, Windows Vista's pretty much the only game in town. And, like playing poker with your Dad's friends, it's a game that will cost you dearly. A few hundred quid at least, depending on your chosen flavour of Vista.

Google Chrome is free. But it's not an OS, right? Well, not quite, and not quite yet. But Google can already provide you with a myriad of apps that can offer everything from calendar and email client, to word processor, presentation app and video player. And with the inclusion of Google Gears, Chrome can work offline too. Just what do you need Windows for?

Google Chrome is far more than a web browser. It's the first tentative attempt at the much-vaunted Google OS. And, wedded to the desktop with a ton of bloat and a barrel-load of ill-feeling, Windows will have to shape up to face the challenge.

See also: Google Chrome browser takes on Microsoft & Mozilla

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