Windows 7, which Microsoft aims to retire as soon as possible, racked up 60 million sales on its initial 10 weeks of launch, leading up to a strong possibility that the overhauled OS would likely bump off its older sibling much sooner than expected.

Most of the migration seemed to represent upgrades, which is cheaper than getting the full Windows 8 package or buying a new PC or mobile device that runs Microsoft's new multi-platform software.

Speaking at the Credit Suisse Annual Technology Conference, Microsoft CFO for Windows Division Tami Reller provided hints that the Windows 8 surge is mostly from existing Windows users, declaring that "Windows 8 is outpacing Windows 7 in terms of upgrades."

In a separate blog by the software giant, the company pointed to the main reason why the new OS is turning out to be a big hit: We built Windows 8 to work great on existing Windows 7 PCs. And we also set out to make upgrading from Windows 7 to Windows 8 super easy."

Analysts, however, were quick to point out that the numbers reported by Microsoft do not necessarily mean that 40 million end-users are currently enjoying Windows 8 as Agence France Presse (AFP) reported that "it's not clear how many people are using Windows 8, because the licenses may be sold to PC makers and not yet in use."

Citing data from research firm StatCounter, Reuters reported too that only about 15 million active PC users around the world are believed to have actually installed or bought Windows 8, or mere one per cent of the estimated 1.5 billion PCs in operation.

Brushing aside the doubts and complaints of apps shortage in Windows Store, Microsoft also reported that its apps revenues since the Oct 26 launch already clocked more than $25,000, adding that "a lot of great new apps have been added to the Windows Store since launch."

"There were more apps in the Windows Store at launch than any other app store at their launch and since then, the number of apps in the Windows Store has doubled," the new Microsoft blog said.

These latest indications, according to Peter Bright of ArsTechnica, seemed to suggest that "Windows 8's launch is far from a failure and that the PC market isn't dead yet," pointing too to the total number of users attributed to Windows' chief rival, Apple's OS X.

As of the latest count, an estimated 66 million global users are listed in the OS X universe, Mr Bright said.

"The PC market may not have exploded the way some OEMs and retailers might have hoped, but it certainly hasn't collapsed just yet," he added.