These are exciting times in Web-based computing, with Microsoft and Google going toe-to-toe on more than just the search engine front.

Yesterday, Nov. 17, Microsoft said Azure, the cloud-based operating system, would be ready for enterprise consumption as soon as Jan. 1, 2010. That's less than six weeks away!

I wrote earlier today how Microsoft stunned folks by embracing open source for Azure. I believe this openness is a weapon Microsoft will wield as it attempts to lure businesses from Google Apps, or at least keep them from going there outright.

But Google isn't going to let Microsoft's Azure have all the high-tech news glory this week. No, the search engine giant has other plans.

Yes, I'm writing to confirm what everyone else has reported: Google will preview its allegedly lighting-fast Chrome Operating System Thursday, Nov. 19.

Here's the invite text:

"Tomorrow we're holding a small press event in Mountain View to update everyone on our progress with Google Chrome OS, give an overview of the technology and provide launch plans for next year. Note that this is a follow-up to the announcement we made in July. Sundar Pichai, Vice President of Product Management and Matthew Papakipos, Engineering Director for Google Chrome OS will be hosting the event."

Pichai spoke rather vaguely about Chrome OS at the Web 2.0 Summit in October, noting that users of netbooks and other devices running Chrome OS won't need to install, tune or maintain the software on PCs.

"In our model ... they don't manage software, they don't manage data, everything is in the cloud," Pichai said. You should be able to take a Chrome OS netbook, get back your windows, get back your state and go.

Azure meanwhile seems much richer, or more complex, depending on how you look at it. My eWEEK colleague Nicholas Kolakowski captured Azure's essence here, courtesy of Ray Ozzie:

""At its core, Azure is Windows--Windows Server," Microsoft Chief Software Architect Ray Ozzie said during a keynote speech on Nov. 19. The Windows Azure platform consists of three parts for creating Web applications and services: Windows Azure, an operating system as a service; SQL Azure, a relational database in the cloud; and .NET services, which provide secure connectivity and federated access control for applications.Combined, Microsoft hopes that the platform will allow it to gain substantial market share against Google, Amazon.com and others making forays into the enterprise-cloud platform environment. Ozzie also introduced a subsystem of Azure, code-named "Dallas," that will function as an open catalog for public and commercial data, as well as a uniform discovery mechanism for that data."

This makes Google's Chrome OS announcement well timed, but it has a lot to live up to, in my opinion. Azure appears to be so far along, raising the question: What will Google have to wow us with?

Indeed, analysts from Collins Stewart already see Google as in the doghouse with the impending arrival of Azure. Sandeep Aggarwal wrote today:

"We view the launch of Windows Azure as a negative for Google. In our view, enterprise CTOs are focused on 3 aspects when it comes to adopting new technology platforms/apps, i.e. familiarity, compatibility, and security. These aspects favor MSFT more than GOOG. As long as MSFT did not have a game plan for cloud, GOOG gained good traction and lots of buzz. However, in backdrop of MSFT's cloud offerings, the going will get tougher for Google Apps in our view."

More than that, Microsoft has an installed base of 1 billion of Windows users, many Windows Server users and Microsoft Office, which shames all others in terms of user base.

Net-net, with Microsoft arriving in the cloud, albeit later than Google, Amazon.com, Salesforce.com and others, what is to stop it from taking the cloud mantle from these companies in their respective spaces -- cloud collaboration, cloud infrastructure and cloud business apps -- within a couple of years?