More than two in five (42 percent) of the world's PCs will be running Windows 7 by the end of the year says Gartner.

According to the research firm, by the end of this year, 94 percent of new PCs will be shipped with the latest iteration of Microsoft's operating system.

"By the end of 2011, nearly 635 million new PCs worldwide are expected to be shipped with Windows 7," research director at Gartner, Annette Jump, said.

Gartner said the surge in machines running Windows 7 has been helped by firms overhauling their machines and moving to the new platform.

"Many organisations have been planning their deployment of Windows 7 for the last 12 to 18 months, and are now moving rapidly to Windows 7."

Gartner believes the US and Asia will be responsible for the majority of the roll-out of Windows 7 to firms. "Economic uncertainties" in Western Europe will result in a slower deployment in this area.

However, the research firm doesn't believe smaller operating systems including Chrome OS, Android or webOS, will obtain "significant market share on PCs in the next few years".

Instead, Gartner said the OSs will need to gain a strong marketbase on "emerging client devices such as Web books and media tablets", first.

"Even then, it is unlikely that they will have any impact on Microsoft and Windows OS's hold on positions on traditional professional PCs in the time frame of the current forecast. This is because of application compatibility issues and the high proportion of Windows-specific applications within many enterprises."

Apple's Mac OS was on four percent of new PCs shipped worldwide, up from 3.3 percent in 2008. Furthermore, its expected the OS will feature of 5.2 percent of new PCs by 2015.

"The adoption of Mac PCs and Mac OS is a result of Apple's ability to grow well above the market average in the last 12 to 24 months, thanks to its ease of use from the user interface (UI) point of view and ease of integration with other Apple devices, such as the iPhone, iPad, iPod touch and the existing Apple ecosystem of applications and programs," Jump said.

Gartner also said Linux would remain "niche over the next five years" accounting for less than two percent of the PC operating system market because of the "remaining high costs of application migration from Windows to Linux".