A .winmd is a file used by Windows 8 WinRT (Windows Run Time). winmd stands for Windows Meta Data file which is the same format used by the .NET framework for the CLI (common language interface). As such it can be viewed by .NET tools such as Reflector and the ildasm tool packaged with .NET. You can find these files in various places but one command place is c:\Windows\System32\WinMetadata.
These files are focused on Windows store apps but it doesn’t preclude you from using them in a traditional desktop app. To do so you need to do the following to your desktop application in order to leverage functionality in these APIs.
1. Unload your application. Edit the project file and add the tag near target version, “<TargetPlatformVersion>8.0</TargetPlatformVersion>”.
2. Reload your project. You will need to add a reference to the following DLLs.
C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.5\WindowsBase.dll
3. Now you will be able to leverage functionality provided by the WinRT framework, such as camera, NFC, etc.