You'll need to have your original disk ready. (In Word2007, you don't
need to have your disk on hand.)
In Start > Control Panel > Regional and Language Options, click the
box for something like "Complex Scripts." Choose the tab for
"Languages" or "Keyboards" (I don't remember the 2003 details), and
tell it that you want (one of the many available varieties of)
Arabic.
After you've made all your choices and followed the instructions, in
the Status Bar at the bottom of your Desktop screen, you'll see you
now have a new icon near the right end. It should say EN (for
English). Click on that and you'll have the choice of switching to
Arabic. (The keyboard shortcut is probably LeftAlt + Shift, which
toggles/cycles the installed languages.)
If your cursor is in a Word document when you change scripts that way,
then you can open the On-Screen Keyboard (which is hidden under Start
All Programs > Accessories > Accessibility, but you can put its icon
in the Start menu). Be sure the AR icon is showing (because you're in
a Word document set to AR); then when you hover your cursor over the
On-Screen Keyboard, it shows you the letter for each key. You can then
type by clicking on the image, or by typing on the keyboard.
(I forget how to type the vowel points, but you probably won't need
them, right?)
