A4 Power Steering

[Seehack@aol.com]

I noticed some rubbing sound early morning when I turned my wheels and also
soft whinny sound from the engine area the few days.  Car drives OK.  Tonight
I checked under the hood (since no indication from the display something is
wrong) and found the power steering reservoir is below Minimum mark.  

Any idea if the power steering is screwed ?  Another thing is what kind of
power steering fluid can I used other than Audi 0000.... which most shops
don't carry except Audi dealers who doesn't open on weekends.  What could
cause the power steering fluid to run out ?

TIA.  Appreciate it.