Just to clarify -- you said below
but alsowhen i open the .doc file directly from the location it is stored on server, everythink is ok.
Is the file corrupted in your files_dir when you open it directly on the server?and there is no difference if i open the file directly or download it and then open.
Unfortunately I don't have a Windows machine to test with at the moment, so this will have to involve some investigation on your part -- but I'd suggest saving the file to disk and doing a binary compare against the original file as it should have downloaded. It's possible that PHP warnings are getting inserted into the document somehow; try disabling the display of PHP warnings and errors in your system's php.ini and redirect them instead to a log file. Then check to see if the download is resulting in any errors or warnings.
I'm at a loss for any reason that .doc files would fail where .pdf files would work; is the .doc file larger than the .pdf files that succeeded?
Open Journal Systems Team