What do you do if you can't see any fonts in Windows Explorer or the start menu?
Open explorer from the taskbar shortcut or the desktop, click in the address bar, type CMD.exe, and then you'll have a command prompt to follow the other instructions in this thread.
But that may not fix it until you reboot, and you may no be able to reboot without the start button showing anything . . . so, in the same command prompt, when that scan is done, type:
shutdown /t 0 /r
Which will reboot your computer without a countdown.