WMF is used for the following file types: MPEG, WMV, MP4, MOV, M2TS. For other file formats, such as AVI and MKV, the Microsoft players are (in most cases) able to display subtitles. You can download a third party software and check if it helps. Search using your favorite search engine for more information. Note: Microsoft cannot guarantee that any problems resulting from the use of Third Party Software can be solved. Using Third Party Software is at your own risk. Please check if suggestions on the following thread works: http://social.technet.microsoft.com/Forums/en/w7itpromedia/thread/49db6282-8a5b-4ca2-bee0-cb870904ba1f