I found a solution.
The problem
So the problem is that Helvetica Neue somehow became the system font for Windows. As it is the system font, it will also be shown on some websites that default to the Windows system font. As it is the system font, it is tied to core processes of the operating system UI, and therefore it is impossible to remove the font even in Safe Mode (file is being locked by a system process that persists even in a minimal boot environment).
So what do we need to do?
So what we need to do is to reset the system font on Windows. Let's restore it to the Segoe UI font.
The solution:
- First let's create a registry file to reset the system font. Open Notepad.
- Copy and paste this:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Fonts]
"Segoe UI (TrueType)"="segoeui.ttf"
"Segoe UI Bold (TrueType)"="segoeuib.ttf"
"Segoe UI Italic (TrueType)"="segoeuii.ttf"
"Segoe UI Bold Italic (TrueType)"="segoeuiz.ttf"
"Segoe UI Semibold (TrueType)"="seguisb.ttf"
"Segoe UI Light (TrueType)"="segoeuil.ttf"
"Segoe UI Symbol (TrueType)"="seguisym.ttf"
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\FontSubstitutes]
"Segoe UI"="Segoe UI"
- Save the file with a .reg extension on your desktop - for example as RestoreSegoeUI.reg
- Double-click it to run it. If prompted by User Account Control (UAC), click Yes to allow the changes. A warning will appear asking if you want to continue; click Yes to proceed.
- Restart your PC.
- Now the font in your browser should be normal again (Segoe UI).
- Go to C:\Users\YOUR_USER_NAME\AppData\Local\Microsoft\Windows\Fonts and delete Helvetica fonts. You shouldn't get no error anymore.