Raw file formats are extremely popular in digital photography workflows because they offer creative professionals greater creative control.
When it comes to a free software/codec that allows you to view the Raw file shot from DJI Phantom Drone then Adobe DNG Codec 2.0 is a good choice. Visit this link supportdownloads.adobe.com/support/downloads/new.jsp to download the codec (Adobe DNG Converter 10.0 for Windows), install it on your PC.
The free Adobe DNG Converter for Windows easily translates raw files from DJI Phantom drones. You also can download the free complete DNG Specification (PDF, 486k) file. DNG is supported by the following Adobe software versions: Photoshop CS to Photoshop CC, Photoshop Elements 3 to Photoshop Elements 12, and all versions of Lightroom.
A restart is required after the installation then you are good to go. All of your .DNG Raw files can be view via Windows Explorer now.