Mesa,
You may change the keyboard by following the steps outlined below:
1> Control Panel -> Regional & Language Options -> Keyboards & Languages
-> Change Keyboard -> Add
<<Choose the Arabic keyboard>> Select "Ok" and exit.
2> Below in the task bar in the lower right hand corner, there should be a
two chracter representation of the langugae of your current keyboard. If it
is not "AR", click on it and check "Arabic". The key board is now changed to
Arabic.
Hope it helps. Feel free to post a quesdtion if the instructions are not
clear or if you have other doubts.
Reards,
Vinay