As of SONAR X3d, SONAR’s video engine defaults to using Microsoft’s Media Foundation framework, rather than DirectShow. This fundamentally improves the way video files are loaded, played, edited and exported in SONAR. Media Foundation generally supports most older formats supported by DirectShow as well as many newer formats such as H264 video.

As a result of this change, users running a Windows N version of Windows 7, Windows 8 or Windows 10 may experience an issue when launching SONAR indicating they must re-install due to a missing MF.dll component.

The reason this happens is because these versions of Windows don't include the Media Foundation DLL itself which other apps may rely on besides Windows media player. They also don't include all the new codecs required for video support.

You can read more about the Windows N versions here:
http://windows.microsoft.com/en-us/windows7/products/what-is-windows-7-n-edition
http://windows.microsoft.com/en-gb/windows-8/n-editions
 

Resolution:

Fortunately this problem can be resolved by downloading a feature pack that includes the missing components. The feature pack installs the following along with other components:

• Media Foundation: Provides support for content protection, audio and video quality, and interoperability for digital rights management (DRM).
• MPEG, WMA, AAC, and Dolby Digital audio codecs: Enables playback of digital audio content such as MP3, WMA, MPEG-2 audio, AAC audio, and AC-3 audio.
• VC-1, MPEG-4, and H.264 codecs: These "standards-based codec components," as they are collectively called, enable Windows 8 software such as Windows Media Player to support activities that include playing back and creating multimedia files that are encoded with standards-based codecs.

Windows Media Feature Pack for Windows 7N: http://support.microsoft.com/kb/968211
Windows Media Feature Pack for Windows 8N: http://support.microsoft.com/kb/2703761/sr-cs
Windows Media Feature Pack for Windows 10N: http://support.microsoft.com/kb/3010081