Well I removed the hard disk from the notebook and connected it via SATA to USB adaptor to my main computer. I then had to take ownership of all the seg*.ttf files, and to be on the safe side, the sym*.ttf files. From Windows Explorer I would have to take ownership one-by-one. The quickest way was to launch an Command Prompt as Admin and then issue these commands:
where J was the letter assigned to the hard disk and SOTIRIS is the computer (system) name.
takeown /S SOTIRIS /U SOTIRIS/Administrators /F seg*.ttf
takeown /S SOTIRIS /U SOTIRIS/Administrators /F sym*.ttf
Unfortunately I didn't know of a quick way to add modify permissions, so I had to open the fonts folder in Windows Explorer, search for seg*.ttf and modify permissions from right-click -> Properties -> Security -> Edit and make sure Administrators have all permissions set. This had to be done one-by-one file, and then delete the results. I then had to search for sym*.ttf and repeat the procedure. After deleting all the relevant fonts, I had to copy them back from my main computer working installation, so I issued this command in the elevated command prompt:
Then I put the disk back into the notebook and booted into Windows 10. I launched IE 11 and navigated to MSN. Sure enough it worked!
copy C:\Windows\Fonts\seg*.ttf J:\Windows\Fonts
copy C:\Windows\Fonts\sym*.ttf J:\Windows\Fonts
Because of all this trouble involved to fix it, I recommend to avoid installing Linux (or any other OS) fonts in Windows.
I'll mark it as solved, but if anyone knows of an easier way to fix it or how to install Linux fonts in Windows 10 without the missing symbols symptoms, I would like to read about it. Thank you in advance!