Well what I know that in order to swtich from english to arabic you should press the right ALT-Shift

However, I dont know why in words I have to press CTRL+SHIFT

any idea?

hmm.....i checked Words to double check.....

both commands work....

Alt + shift

Ctrl + shift

but in Ctrl case....left side for english and right side for arabic...beside... using control it will automatically...go from left to right and the other way around.

Though both of them work anywhere....difference is that to use ctrl+shift it has to be within a text box...or edit.

I think that you can change the settings of that from the "Language & Reginoal Settings".