KB5077181 was released about a month ago as part of the February Patch Tuesday rollout. When the update first arrived, users reported a wide range of problems, including boot loops, login errors, and installation issues.
Microsoft has now acknowledged another problem linked to the same update. Some affected users see the message “C:\ is not accessible – Access denied” when trying to open the system drive.


But it can boot into Windows, which is also on the C drive? So it’s not locking users out of the C drive, it’s locking users out of parts of the C drive.
The boot process isn’t an user process, Windows would still be able to use the C:/ drive for itself, for every other user software though, that’s another story…
So only the user process is locked out of the C drive, not the boot/system. Fortunately, the way Windows 10/11 works by default, if you sign into a Microslop account, it backs all that stuff up to OneDrive. At least your documents. And no one’s saying it’s not bad, it just seems like most affected individuals will be able to go about most of their day. I have a Mac, so I
don’t need to worry about any of thishave separate issues to worry about.Having OneDrive wouldn’t help as you still won’t be able to use programs as a user, which is pretty much the reason we use computers in the first place, this bug effectively makes whole computers glorified paperweight in the meantime.