Thanks God. I got the solution. I am just writing it in detail so that if anyon faces the similar problem,it might help. I called one of my friends, he instructed me on phone and it,s fine now.
I went to Control Panel, Regional and Language Options, then clicked the Regional Options tab and changed it from English(UK ) to English( United States), then clicked the Languages tab, there is option Text services and input languages, i clicked the option details here and selected English(US) as defaut input language, then from Installed services options i selected the Keyboard US and clicked Add... and it,s all done. keyboad is OK now. ( I am sorry if i confuse someone by this description,in practice it was so simple). I think this problem is specific to Arabic English keyboard used in middle east, thats why i was not able to get any clear response in the forums.
I will wait for your feedback.