Answer by Angel for Windows 8.1 missing font files after restart

This has happened to me twice now, both times after a failed font installation. The problem occurs not only after a restart, but also after logging out of and back into a Windows account.

I ended up solving it with a bit of a scattershot approach (mostly out of frustration), but everything seems to be working now after multiple reboots. You'll need a copy of a C:\Windows\Fonts directory from a PC that is not suffering from this problem.

1. Copy the contents of a C:\Windows\Fonts directory from a PC that is not suffering from this problem and paste them into the afflicted C:\Windows\Fonts directory.
2. Open up Regedit.
3. Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\
4. Export (just in case) and then delete the entire Fonts group. I also deleted the groups Font Management, Font Drivers, FontLink, FontMapper, and FontSubstitutes, though I re-added them later and suspect they were unrelated.
5. AGAIN copy the contents of a C:\Windows\Fonts directory from a PC that is not suffering from this problem and paste them into the afflicted C:\Windows\Fonts directory.
6. Reboot.