When Google (NASDAQ:GOOG) first introduced its Chrome browser, it only looked like an operating system. Soon, it'll actually be one.

"Google Chrome OS is an open source, lightweight operating system that will initially be targeted at netbooks," Vice President of Product Management Sundar Pichai and Engineering Director Linus Upson wrote in a blog post from last night. "Later this year we will open-source its code, and netbooks running Google Chrome OS will be available for consumers in the second half of 2010."

From whom, we don't yet know. The Big G says only that Chrome OS will be made to work with both x86 and ARM processors. Intel (NASDAQ:INTC), Advanced Micro Devices (NYSE:AMD), and ARM Holdings (NASDAQ:ARMH) are among those likely to benefit.

Dell (NASDAQ:DELL) and Hewlett-Packard (NASDAQ:HPQ) have a tougher decision to make. Offering Ubuntu Linux as an option for your netbook customers is one thing. Selling a Gbook is another. There's no way Microsoft (NASDAQ:MSFT) can be pleased about this, especially given emerging evidence that Windows is struggling to compete as a netbook OS.

Many observers foresaw Google's interest in entering the netbook market, including yours truly. Yet one thing about this announcement surprised me: Chrome OS and Google's Android smartphone operating system will remain distinct.

What's not surprising is that Chrome OS will be a beginning, rather than an end. "We hear a lot from our users and their message is clear -- computers need to get better," Pichai and Upson wrote. Notice the language. Google thinks "computers," not "netbooks," need to improve.

Google wants Chrome OS to be a comprehensive operating system, a gateway to cloud computing -- and a way to replace Windows.

We've got two monopolies here, engaged in a global conflict that stretches from productivity software to browsers to search engines, and now to operating systems. The stakes don't come any bigger. I've already bet on Google for my personal portfolio. I've also recommended that our Motley Fool Rule Breakers subscribers buy shares. Others, like my peers over at Motley Fool Inside Value, like Microsoft's price and position.

With whom do you side? Cast your vote, and then share your rationale with us in the comments box below.

Apple is a Stock Advisor selection. Microsoft, Intel, and Dell are Inside Value picks. Google is a Rule Breakers recommendation. Try any of our Foolish newsletter services free for 30 days.

Fool contributor Tim Beyers had stock and options positions in Apple and Google at the time of publication. Check out Tim's portfolio holdings and Foolish writings, or connect with him on Twitter as @milehighfool. The Motley Fool is also on Twitter as @TheMotleyFool. The Fool's disclosure policy salutes you.