SAN FRANCISCO, US (AFP) - Microsoft's new-generation Windows 7 operating system hit the ground running, with US sales in its opening days blasting past those of its Vista predecessor, according to NPD Group.

Sales of Windows 7 in the days following its October 22 release were 234 percent higher than those posted by Vista when it was released into the market, the market research firm reported on Thursday.

"Microsoft's program of early low-cost pre-sales, high visibility marketing, and aggressive deals helped make the Windows 7 software launch successful," said NPD vice president of analysis Stephen Baker.

"In a slow environment for packaged software Windows 7 brought a large number of customers into the software aisles," he said.

Revenue from Windows 7 sales during its initial days in the market only surpassed Vista by 83 percent due to price discounts and a lack of promotion for an Ultimate version of the new operating system, according to NPD.

The Windows 7 launch also gave a bump to personal computer (PC) sales, which nearly doubled from the previous week and were 49 percent higher than the same period a year earlier, but Vista's launch gave PC sales a bigger boost, NPD said.

"A combination of factors impacted Windows 7 PC sales at the outset, but the trajectory of overall PC sales is very strong leading into the holiday season," said Baker.

Microsoft's much-heralded Windows 7 went on sale around the world in October as the US software giant rebooted after the disappointment of its previous generation operating system Vista.

Windows 7 made its global debut to generally good reviews with most technology analysts and users who tested a demo version praising it as a significant improvement on the much-maligned Vista.

Analyst Rob Enderle of Silicon Valley's Enderle Group said the Windows 7 launch was a "big deal for Microsoft."

"Windows Vista was a train wreck," he said.

While computer users may not give much thought to the operating systems that serve as the brains of their machines, they are at the heart of Microsoft's global software empire that runs more than 90 percent of the world's computers.

Microsoft apparently learned a lesson from Vista and worked closely with computer makers, users and software developers while crafting Windows 7.

More than eight million people dabbled with Windows 7 in a beta test phase.

Among the new features in Windows 7 is a redesigned taskbar for launching programs and switching windows, enhanced ability to share files with other PCs, improved photo and video editing software and the ability to stream digital music or video to other devices.

Windows 7 also features Microsoft's latest Web browser, Internet Explorer 8.