You cannot upgrade one language of vista to another with that upgrade disk.
Vista buisness does not allow you to install the MUI packs, these are
available ONLY to Vista ultimate users and another version of vista called
enteprise.
If you do upgrade your business version to Ultimate, you can choose many
languages and you can switch from lanugage to language.. its very nice....
there is also LIP that is a more limited language pack, free for all
versions of windows.. see here.. im not sure it has arabic
see this link>>>>>
http://windowshelp.microsoft.com/Windows/en-US/Help/35a1b021-d96c-49a5-8d8f-5e9d64ab5ecc1033.mspx
for the lip see here
http://www.microsoft.com/unlimitedpotential/locallanguageprogram/default.mspx
Im not sure about LIP in arabic... but that site will guide you to see if
there is one
tell me if this information helps
--
50 Ways to leave your Vista....
CHORUS:
You just format the drive , Clive
Get a New Mac , Jack
Y'don't need that crap toy, Roy
Just get yourself free
Boot from a *nix, Jix
You don't need to discuss much
Install XP, Lee
And get yourself free