Microsoft Corp.’s latest operating system (OS) – Windows Vista – is on track to be installed into 10% of personal computers (PCs) that are currently in use by actual customers. But despite of relative popularity of Vista, the share of personal computers running Windows decreased this year by nearly 1%, whereas Apple’s Mac OS- as well as Linux-based computers increased their relative presence.

According to Net Applications, a provider of various Web tools, the share of PCs with Windows Vista installed that are used to browse the Internet increased to 9.19% in November, 2007, up more than one percent from 7.94% a month before. Consequently, the share of system equipped with Windows XP, Windows 2000 and Windows 98 dropped to 78.37%, 2.97% and 0.76%, respectively.

But the overall market share of Microsoft Windows based PCs decreased by 0.07% in November: from 92.49% to 92.42%, whereas shares of Apple Mac OS and Linux systems increased by 0.22% to 6.80% and by 0.07% to 0.57%, respectively. In fact, Windows has lost 0.91% market share from January, whereas Mac OS X and Linux gained 0.58% and 0.22%, respectively.

The nearly 1% market share drop in about 11 month is not a catastrophe for Microsoft, which operating systems still control 92.42% of the PCs currently in use. However, the trend may continue going forward as Linux-based low-end personal computers along with cheap systems for developing countries gain market share.

But what is much more important for Microsoft than simplistic computers with limited capabilities is that Windows has lost 2.82% of the market since December, 2005, when it was used on 95.24% of systems. Meanwhile, Apple’s Mac OS increased its share by 2.45%, by gaining from 4.35% to 6.80%.

It was unclear at press time how many computer systems Net Applications tracked in November, 2007.