joomla index.php page is automatically redirected with "not found" error
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First of all, I am not familiar with Joomla and PHP. I am trying to copy a joomla website to a sub domain of a website: http://sub.domain.com. database and everything seems fine. When I access http://sub.domain.com, the website is automatically redirected to: http://sub.domain.com/en/index.php and the error is:

    The page cannot be found
    
    The page you are looking for might have been removed, had its name changed, or is temporarily unavailable.
    Please try the following:
    
    Make sure that the Web site address displayed in the address bar of your browser is spelled and formatted correctly.
    If you reached this page by clicking a link, contact the Web site administrator to alert them that the link is incorrectly formatted.
    Click the Back button to try another link.
    HTTP Error 404 - File or directory not found.
    Internet Information Services (IIS)
    
    Technical Information (for support personnel)
    
    Go to Microsoft Product Support Services and perform a title search for the words HTTP and 404.
    Open IIS Help, which is accessible in IIS Manager (inetmgr), and search for topics titled Web Site Setup, Common Administrative Tasks, and About Custom Error Messages.

Yes, I deploy the joomla site on an IIS server but I am sure it is running both for php as well as asp.net.

Any idea about this auto-redirection and how can I solve this?

Thanks in advance. 