Microsoft faces a multi-million dollar, class action lawsuit from US citizens who claim they lost data or suffered ‘damage to software or hardware’ after upgrading to Windows 10.

The case, filed last Thursday, is seeking for Microsoft to pay more than $5m in damages, excluding costs and interest, to the 100-plus members of the class action suit.

“Many consumers have had their existing software and data rendered inoperable by the Windows 10 installation,” according to the filing, made to the US District Court for the Northern District of Illinois.

“As a result of its failure to exercise reasonable care, defendant distributed an operating system that was liable to cause loss of data or damage to hardware.”

The complaints relate to the free Windows 10 upgrade that Microsoft offered to Windows 7 and 8 users until July 2016, one year after Windows 10’s launch.

SEE: Windows 10: The 10 biggest controversies and surprises in 2016

The court documents cite specific cases where residents of Illinois been affected. In one instance, plaintiff Howard Goldberg attempted to download the Windows 10 upgrade, but after three attempts “Goldberg’s computer was damaged, and Windows 10 was not actually downloaded and functional”, the filing says.

Microsoft told Goldberg he would have to pay for assistance as his machine was out of warranty, the document claims, and he had to pay a third party to make his PC usable.

Another plaintiff, Stephanie Watson, lost data after her machine was upgraded to Windows 10, the filing states, and “had to purchase a replacement machine in order to have a fully functioning computer”.

The lawsuit seeks damages for all Illinois residents who suffered loss of data or damage to their computer within 30 days of a Windows 10 upgrade. The suit goes as far as saying that “consumers have had their hard drive fail because of the Windows 10 installation”.

The filing also raises the issue of plaintiffs being upgraded to Windows 10 without knowingly accepting the upgrade.

“A great number of people have installed the Windows 10 system inadvertently or without full realization of the extent of the download,” the document states.

“The Windows 10 system often installs itself without any action being taken by the consumer. The first the consumer knows of the installation is a message on the computer screen, ‘DO NOT TURN OFF YOUR COMPUTER WHILE WINDOWS 10 IS BEING DOWNLOADED’.”

Responding to the suit, a Microsoft spokesperson said: “Customers had the option not to upgrade to Windows 10.

“If a customer who upgraded during the one year program needed help with the upgrade experience, we had numerous options including free customer support and 31 days to roll back to their old operating system. We believe the plaintiffs’ claims are without merit.”

Last year, a US small claims court ruled that Microsoft should pay $10,000 to Teri Goldstein, a travel agent based in Sausalito, California, who said an unwanted Windows 10 upgrade made her PC unstable.

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