When user tries to stream and listen or watch audio or video from Microsoft Windows Media Services, or clicks on a hyper-link starts with mms:// syntax, Windows Media Player (WMP) may give the following error message:

Windows Media Player cannot play the file because the specified protocol is not supported. If you typed a URL in the Open URL dialog box, try using a different transport protocol (for example, “http:” or “rtsp:”).


In addition, user may also encounter the following symptoms:

  • When you click the Network tab of the Windows Media Player Options menu, nothing happens.
  • On the Windows Media Player Network tab, the “Streaming proxy settings” protocol listing is empty.

The error does not happen or occur when user plays back the media or content that is stored on a local hard disk drive or connected external mass storage device via USB or FireWire.

The problem is caused by either the wmnetmgr.dll file (located in C:\Windows\System32) is unregistered, the wmsdkns.xml file is corrupted or has incorrect permissions.

To fix the issue, use one of the following resolution methods:

Method 1

Register the wmnetmgr.dll file by using an account that is in the Administrators group. At an elevated command prompt, run the following command.:

regsvr32 wmnetmgr.dll

Method 2

Make sure that (and add in the right if necessary) the user account that is using Windows Media Player has Modify permissions for the wmsdkns.xml file, using the file properties Security tab.

Note: In Windows Vista, the file is located in the C:\Users\Username\AppData\Local\Microsoft\Windows Media\11.0 folder. In Windows XP, the file is located in the C:\Documents and Settings\UserName\Local Settings\Application Data\Microsoft\Windows Media\11.0 folder.

Method 3

Delete the wmsdkns.xml file. Windows Media Player will re-create the wmsdkns.xml file upon deletion.

Note: In Windows Vista, the file is located in the C:\Users\Username\AppData\Local\Microsoft\Windows Media\11.0 folder. In Windows XP, the file is located in the C:\Documents and Settings\UserName\Local Settings\Application Data\Microsoft\Windows Media\11.0 folder.

Another possible reason for the error because the file type association for URL:MMS protocol has not be assigned properly. Here’s the fix for Windows Media Player does not handle URL:MMS stream protocol.

Source: KB940029

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