Microsoft is facing a lawsuit in the US over its heavy-handed attempts to force people into upgrading to Windows 10 that, the plaintiffs claim, caused them to lose data after their upgrades went awry.

The suit filed in the Chicago District Court claims that Microsoft "failed to exercise reasonable care in designing, formulating, and manufacturing the Windows 10 upgrade and placing it into the stream of commerce".

It goes on to claim the software is bug-ridden and not fit for purpose, adding that Microsoft didn't warn people of the risks of upgrading.

"As a result of its failure to exercise reasonable care, [the company] distributed an operating system that was liable to cause loss of data or damage to hardware," the lawsuit claims.

This isn't the first lawsuit regarding Windows 10 upgrades. Last June a woman in California was offered $10,000 after her computer was borked by the update. However, at the time Microsoft claimed it was settling because it was cheaper than fighting and an existing class action suit was filed last year in Seattle.

The first stage will be for the suit to be declared as a class action. This means that anyone in the US who upgraded from Windows 7 (Windows 8 would not be included under this motion) and who has suffered any of the symptoms described within 30 days could join in.

The claim also alleges that Windows 10 "often installs itself without any action being taken by the consumer".

Microsoft invariably takes its time responding to requests for comment over such issues. But it has nevertheless told The Register that "the Windows 10 free upgrade program was a choice designed to help people take advantage of the most secure, and most productive Windows".

The quote continues: "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."