New report details the bugs and issues users experience, and calls for compensation.
Microsoft should compensate Windows 10 users who still experience issues first flagged to it in 2016, according to UK consumer watchdog Which?, with the comparison service demanding the software giant work harder to fix the problems.
More than half of 1,100 Which? members surveyed in March 2018 told the publication they had suffered glitches with the operating system, after a similar number complained about Windows 10 issues two years ago.
The latest survey saw 21% complain about software compatibility after upgrading to the latest operating system, 16% say external devices no longer worked with their PC, and 7% reveal that their email would no longer sync.
Meanwhile, 5% suffered significant slowdowns on their machines, and even PC failure, with nearly half who experienced this paying significant money to have it fixed by a specialist.
Which? criticised Microsoft's free support, saying it didn't go far enough to fix users' issues. It has demanded that Microsoft improve the visibility of its free support services, and Microsoft is meeting with the consumer rights publication to discuss how it can fix Windows 10 issues for free.
A Microsoft spokesperson told Which?: "We want to make sure our customers receive the right support they need to get the best Windows update experience, and we will continue to review customer enquiries and issues on a case-by-case basis to ensure individual help and resolution where possible.
"Windows 10 is the safest and most secure version of Windows and we are glad that Which? shares our recommendation for customers to stay current with the latest Windows updates."
The vendor is also under pressure from Which? to offer free compensation to those who have lost data and files in the process of upgrading to Windows 10 and spent money trying to get them back.
The survey came before the April 2018 Update, and with Windows 10, users must stay current with updates to continue to receive security patches - even if an update could break their computer.
Consequently, Which? has called for Microsoft to issue separate security patches to ensure those running older versions of Windows 10 can ensure their PC is safe from known bugs and hacks.