The official countdown begins as Microsoft said on Wednesday that its numerous tinkering and testing on the new Windows 8 and Windows RT have been completed.

"With RTM (release to manufacturing), we've completed the product development and testing and have officially started handing off the final code to our OEM partners, who are preparing new Windows 8 PCs and tablets they'll introduce," the software giant was reported by The Australian as saying in a blog post.

The blog was personally penned by Steve Sinofsky, the point man for Microsoft's Windows and Windows Live division.

Mr Sinofsky added that the news should also mean that app developers can start finalising their products as the Windows RTM online store will begin accommodating uploads by August 15.

Microsoft is targeting 200 markets for the initial launch of its apps depot, which will first open its doors in the United States and will be followed by rolling inaugurals in the weeks ahead.

August 15 will be the same date that developers can start to download the final version of Microsoft newest operating system, which the tech giant has engineered to work on multiple platforms that span conventional computer systems.

Specifically, Microsoft aims to make further inroads in the mobile computing market that is presently dominated by Apple's iOS and Google's Android.

The company is doing so by offering Windows 8 versions to smartphone vendors, foremost of which is its major partner Nokia, and tablet computer manufacturers.

Microsoft in fact will release its own tablet product called Surface, which will come in two versions that will be powered by Intel and ARM processors. The two tablets will be humming separately with Windows 8 on Intel and Windows RT on ARM.

Windows 8's main attraction, the Metro UI that serves as the platform's gateway to apps, will highlight the company's foray into mobile computing that provides users extension of their fingertips while navigating softwares and the web.

But for Microsoft to establish decent competition level with rivals at the onset, Patrick Moorhead of Moor Insights & Strategy told ComputerWorld that its apps store must contain at least 5000 quality and attractive apps to lure buyers into snapping up Surface and Windows smartphones come October 26, the date the company has set as the commercial release of Windows 8 and its related products.

"Otherwise, Microsoft will have an extremely hard time, if not an impossible time, selling a Windows 8- or Windows RT-based tablet," Mr Moorhead said.

Mr Sinofsky, however, remains upbeat on the commercial prospects of his new product despite reservations aired by tech experts that Windows 8 will be pitted against the vaunted ecosystems of Apple and Google, which between them enjoy apps collection of more than a million.

The Microsoft executive was banking on the amount of participation that Windows 8 had generated on its trial stage, which Mr Sinofsky peaked to an estimated 16 million users worldwide.

He said that Microsoft was "sincerely humbled by the breadth of participation in our pre-release testing."

Yet for tech analyst Michael Cherry, wrapping up the final works on Windows 8 should also mean that more challenges are ahead for Microsoft.

"We need to see the exciting Metro apps that do something, that expose all the features of the OS that Microsoft has just completed," Mr Cherry told ComputerWorld.

In short, between now and October 26, Microsoft needs to ramp up efforts that would ensure users will enjoy rich experience plunging into the world of Windows 8 later this year.