Microsoft Corp appears to be on track to release its new Windows 8 operating system in time for the crucial U.S. holiday shopping season after making a "release preview" of the new code available for download on Thursday.

Windows 8 is the latest version of the flagship product, which still provides almost half of the world's largest software company's profit. It is the first version that will run on tablet computers as well as PCs, providing Microsoft's first real challenge to Apple Inc's iPad.

"The progress Microsoft is making leads me to believe that Windows 8 will be available in time for the holiday season this year," said David Johnson, an analyst at tech research firm Forrester. "I've been using the consumer preview for several weeks, and while it's obvious more finishing work is needed, it has been stable and reliable."

Microsoft's latest release preview is similar to what the software company used to call a "release candidate," meaning the product is all but finished. The next stage is "release to manufacturing" (RTM), when Microsoft hands the code to PC makers such as H-P, Dell and Lenovo to install on new PCs, laptops and tablets.

Based on the timeline for Windows 7 three years ago, Microsoft is on track for full release by October or November, when machines running it will be available in stores. The company has never put a firm date on the release of Windows 8, but says it aims to have a new system every three years. Windows 7 debuted in October 2009.

"Ultimately, our partners will determine when their PCs are available in market," said Steven Sinofsky, the head of Microsoft's Windows unit, in a blog post on the company's site.

"If the feedback and telemetry on Windows 8 and Windows RT (the tablet-compatible version) match our expectations, then we will enter the final phases of the RTM process in about two months. If we are successful in that, then we are tracking to our shared goal of having PCs with Windows 8 and Windows RT available for the holidays."

In the meantime, in order to prevent a drop-off in PC sales, Microsoft said on Thursday that customers who buy Windows 7 PCs between now and January 31 can get an upgrade to Windows 8 Pro for $14.99.

微软似乎会在美国假期购物季发布Windows 8操作系统。微软周四发布了Windows 8的预览版。Windows 8是微软视窗产品的最新版本，视窗产品几乎占微软全部利润的一半。这也是首款可以同时在平板电脑和个人电脑（PC）上运行的视窗系统版本，首次向苹果iPad发出了真正的挑战。

根据三年前Windows 7的发布历程，微软或在10月或11月前正式发售Windows 8系统。微软从未公布Windows 8确切的上市日期，但表示公司希望每三年能发布一个新系统。Windows 7在2009年10月正式上市。