Rick Rashid, Chief Research Officer of Microsoft Corporation, delivers a keynote speech at the 14th Computing in the 21st Century Conference held in north China's Tianjin Municipality, Oct 25, 2012. The conference invited computer specialists and experts to share with the audience the latest trend and achievements in the computing science. [Photo/Xinhua]

BEIJING -- IT giant Microsoft is under fire in China as the company pushes users to upgrade their operating systems to Windows 10.

The pop-up upgrade window does not offer a "decline" option, only a choice to upgrade later. Computers running older versions of Windows will automatically start the upgrade at the recommended time if users ignore the pop-up without selecting the easy-to-miss option to delay or cancel the update.

Yang Shuo, who works at a Beijing-based public relations company, said the sudden update interrupted him while drafting a business plan, which led to cancellation of a meeting for a deal worth 3 million yuan ($457,500).

Yang said he failed to save the draft when his laptop restarted for the update. His clients had left by the time he finally finished the plan.

"Just because I didn't see the pop-up reminder does not mean I agreed," said Yang, adding he did not even know when the installation package was downloaded to the laptop, as he wasn't connected to the Internet when the update started.

Yang is not the only one complaining about the unwanted update. On microblog site Weibo, posts related to Windows 10 reached more than 1.2 million.

"I had ignored all pop-up reminders about the update in past months, but it suddenly started updating automatically," Ning Jiayu, professor at Nankai University in Tianjin, posted on Weibo early on Thursday.

"Can't you stop forcing users to update? Do you know how much work by graphic designers you have ruined?" wrote a graphic designer under the screen name "3jinyeshixin."

Xinhua reporters sent a text message to the Microsoft China office on Thursday, but did not receive a response.

Microsoft technical support staff have posted instructions on the company's official Weibo account for users who want to revert to an earlier version of the operating system.

The company said earlier this month that more than 300 million devices have started using the Windows 10 platform, and the free update will end on July 29.

Experts believe the aggressive update is being pushed as the company tries to secure market share in the face of competitors such as Google and Apple. The company is expected to use Windows 10 as a platform for app development.

Zhao Zhanling, a legal advisor with the Internet Society of China, said Microsoft has not respected users' right to know and choose, especially since the company may eventually profit from the unwanted upgrades.

"The company has abused its dominant market position and broken the market order for fair play," Zhao said.

He said users or consumer protection organizations have the right to file a lawsuit against the company.