So it is supposed to be in Arabic, just not that specific Arabic font, correct?
Your icons are different from the default, so I'm guessing you're running a program to change the system icons. If so, changing the system font is probably another feature of that program, and that's probably what happened.
So... did you install something like that, and if so, what? Also, check its settings (probably a preference pane) and see if it has an obvious "System Font" option somewhere.