http://www.al-sunan.org/vb/showthread.php?t=9231
(Click View, Encoding, More, Arabic (Windows))
This one works with Windows 7:
http://downloads.sf.net/arab/ArabicKeyboard.exe
This one is good too:
http://zsigri.tripod.com/fontboard/arablpk.html
Another option: http://www.youtube.com/watch?v=nU_zAT3RHkQ
How to enable it in your computer (instructions may be slightly different for different operating systems)
Click on Start
Click on Control Panel
Click on Clock, Language, and Region (or whatever link has language/keyboard in it)
Click on Region and Language
Click on Keyboards and Languages
Click on Change Keyboards
Click Add
Click on Arabic (Saudi Arabia)
Put a check mark in the box beside Arabic 101
(Click Preview to see which Arabic letters correspond to which English ones – however the best way to learn is to type a lot in Arabic)
Click OK
Click Apply
(Click on Language Bar to make sure the box that says “Show text labels in the language bar” is checked and the “Docked in the Taskbar” button is clicked – Apply)
(Advanced Key Settings should show that holding the Left Alt button and shift button at the same time changes the language)
After these steps there should be a small box with EN on it in the task bar.