Hi Sepi,
Thank you for posting your query in Microsoft Community.
I can imagine the inconvenience you have experienced. Don’t worry; we will give our best to help you.
Have you made any changes to the computer prior to the issue?
I would suggest you to follow these methods and check.
Method 1: For applications that are not supporting Unicode, you might have to change the system locale which determines the default character set (letters, symbols, and numbers).
See this link: http://windows.microsoft.com/en-US/windows7/Change-the-system-locale
Also refer the link mentioned below, and check if it helps:
http://windows.microsoft.com/en-US/windows7/Install-or-change-a-display-language
Method 2: Reset “add an input language” settings.
a. Open Regional and Language Options by clicking the Start button, clicking Control Panel**,**clicking Clock, Language, and Region, and then clicking Regional and Language Options.
b. Click the Keyboards and Languages tab, and then click Change keyboards.
c. Under Installed services, you will find Persian language, click on it, once you click on it on the right hand side you will get an option to remove the language. Click on it, click on Apply and Ok.
d. Restart the computer, install the Persian Language and check with the issue.
Hope this will be helpful. If you still have further queries, please reply us and we will be happy to help you.