Preferred font styles

Hi!
 
Can anyone tell me which font styles are preferred for the following
languages:
 
Russian
Urdu
Arabic
Persian/Farsi
Kurdish/Sorani
 
We are developing a multilingual website with dynamic content, and we
don't always know which language being displayed. Is there a font that
covers all the characters needed for these languages? Arial Unicode (too
big for download...)? Any font styles that are standard in windows
98/2000/XP?
 
Any help appreciated!
 
Thanks!
 
Lill Therese