Microsoft (Nasdaq: MSFT) launched a search engine, so Google’s (Nasdaq: GOOG) releasing an operating system (OS). It looks like war.

Google’s Chrome OS shares the same name as its browser, though it will operate independently. It’s expected to be available in about a year. Google hasn’t announced a price, though most experts expect it to work like most of Google’s products, which are free but make money with advertising.

Chrome OS targets intensive web users who seek “speed, simplicity and security,” according to a Google blog. The operating system is “lightweight,” meaning it can be used on less-powerful laptops and netbooks. Microsoft’s products tend to be more memory-intensive and perform best with the fastest processors. Chrome automatically incorporates security patches, something Microsoft’s operating systems don’t do.

Google’s new operating system represents both a shot at Microsoft and a potentially lucrative new revenue stream. The firm’s attempts to monetize its YouTube video service, which it snatched up for $1.65 billion back in late 2006, have yet to deliver — neither have its other software ventures. Almost all of Google’s revenue, 97%, comes from its wildly popular “AdWords ” advertising platform.

Does this spell doomsday for Microsoft? Probably not.

Part of the reason is that Google’s new operating system is designed for netbooks — small laptops primarily used for surfing the web. So even if it gains widespread acceptance, it would only get a small piece of the pie.

The other problem is that Microsoft controls the incumbent operating system on the vast majority of the world’s computers. It’s on your computer when you take it out of the box. Swapping operating systems, after all, is a technical hassle that’s typically undertaken only by hard-care computer nerds. So Google has to cross a deep moat to penetrate the operating system castle — assuming Google can figure out how to monetize it.

For investors, the news is interesting but not actionable. If you’re looking for a reason to short Microsoft or buy Google, keep looking. And bear this critical fact in mind: At the speed the tech world moves, some other player may come in and change the playing field by the time Chrome is released.