Recover Windows 10 when login screen flickers and doesn't load

Question

Recently a font installation on my Windows 10 system failed. This seemed to have messed up the system font, as on the next reboot, filenames and most UI menus appeared in hieroglyphs.

I followed the instructions on Windows 8.1 missing font files after restart: I replaced the fonts in the C:\Windows\Fonts directory with the default ones and deleted the registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Fonts. As a result, the next time I wanted to boot, I couldn't even log in anymore. The login screen never appeared, instead I saw a screen with the loading spinner, that flickered 2-3 times per second. Safe mode in all its variants makes no difference.

From the startup recovery command line, I restored the backed-up registry key and also tried to adopt a friend's key and fonts directory 1:1, both to no avail. Now, I'm faced with an unusable Windows 10 System, all a result of installing a broken font. Unfortunately, I don't have restore points, so I would have to reinstall my entire Windows if I can't fix this.

Is there a way to repair the broken login screen? Unfortunately I don't even see a way to run PowerShell from the recovery CMD (to follow this answer which seems very promising). At least I managed to back up my data from that CMD.

Answer 1

Very nice, I could finally solve the problem.

After researching for a while, I found out that the registry that I edited from the recovery command line was not the actual one used on the computer. I had to load the registry hive HKEY_LOCAL_MACHINE\SOFTWARE (with a different keyname, e.g. SOFTWARE2) from C:\Windows\System32\config\SOFTWARE.

Then, replacing the entire HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Fonts key and the C:\Windows\Fonts directory with working ones of a friend would do the job -- I could boot again and log in normally.

I should really start to use Windows recovery points.