Hi all,
I have WindowsXP and the same message appears, when I try to install font on account without administrator privileges. Maybe that..?

Yes, you must have admin rights to install font this way (I know, it's totally stupid!).
Solution N°1 : get admin rights
Sulution N°2 : install a font management program (but you may need admin rights once to install the software)

It's not ever necessary to have admin rights to install a font but the admin can to forbid for a login to have the possibility to install a font (or something else).
The best is to contact you admin or the people that rule the rights of your computer.

You need to download a .ttf to .fon converter. Then it should work.