Please read Change your font settings Microsoft article (applies to windows 8 as well).
Doing Restore default font settings does not change installed fonts, only removes any changes that you've made to your display settings (Control Panel\All Control Panel Items\Display
) including all manual changes that you've made to your display settings.
In other words:
Restore default font settings in Control Panel\All Control Panel Items\Fonts\Font settings
restores default data for values under this registry key:
HKEY_CURRENT_USER\Control Panel\Desktop\WindowMetrics
Example:

For instance, I have changed size of all items in Control Panel\All Control Panel Items\Display
to Medium - 125 % for the sake of my old tired eyes:
==> reg query "HKCU\Control Panel\Desktop" -v LogPixels
HKEY_CURRENT_USER\Control Panel\Desktop
LogPixels REG_DWORD 0x78
while Windows default value is Smaller - 100% (default):
==> reg query "HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\FontDPI"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\FontDPI
LogPixels REG_DWORD 0x60
Indeed, 0x78
(decimal 120) is exactly 125 percent from 0x60
(decimal 96):
==> set /a 0x60 * 125 / 100
120