Log on as administrator. Open command prompt as admin.
attrib -r -s %systemroot%\fonts
takeown /f "%systemroot%\fonts" /r /d n
(optional - gives administrators full rights on the fonts folder): icacls "%systemroot%\fonts" /grant administrators:F /t
You can now add or change permissions on the Fonts folder like any regular folder.
Give user(s) modify access to %systemroot%\Fonts
icacls "%systemroot%\fonts" /grant USERNAMEorGROUP:M /t
Give user(s) modify access to %systemroot%\system32\FNTCACHE.dat
icacls "%systemroot%\system32\FNTCACHE.dat" /grant USERNAMEorGROUP:M /t
Give user(s) modify access to HKLM\Software\Microsoft\Windows NT\Current Version\Fonts