Windows 7 will be running on 42 percent of PCs by the end of the year - a big jump from last year, according to Gartner research.
The uptake is helped by businesses starting to spend more to refresh their PCs, with 94 percent of new machines shipping with Windows 7, Gartner said.
"By the end of 2011, nearly 635 million new PCs worldwide are expected to be shipped with Windows 7," Annette Jump, research director at Gartner said. "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."
The US and Asia are expected to drive enterprise sales the most, while "economic uncertainties" mean Western Europe will see a slower roll out.
As of July, separate research from Net Applications said Windows 7 had 28 percent of the market, while XP remained at just under 50 percent.
Windows will hold onto its market dominance for years to come, Gartner added.
The boost in PC sales has helped Apple, which has managed to grow sales of its Macs above the rest of the computer market over the past two years. But Gartner said Mac OS was still on only four percent of new PCs last year, up from 3.3 percent in 2007 with growth of 4.5 percent expected this year.
Linux's share of the market will stay under two percent, while Gartner didn't think alternative OSes had much of a chance.
"Gartner does not expect Chrome OS, Android or webOS to get any significant market share on PCs in the next few years," the analyst firm said.
In order to succeed, such platforms will need to grab market share on 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," it added.
"This is because of application compatibility issues and the high proportion of Windows-specific applications within many organisations."
However, Gartner added that balance is quickly changing, and as many as half of applications are already "OS-agnostic". As much of that change has been in the consumer market, not in businesses, such alternative OSes have a better chance of immediate success there, Gartner added.