My first choice would be struct initialization the normal way.

But if you want to copy a byte array, it is done something like this.
Code:
   const unsigned char init[] =
   {
      0x28,0x00,0x01,0x00,0x25,0x00,0x00,0x00,
      0x00,0x20,0x00,0x00,0x00,0x00,0x00,0x00,
      0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x10,
      0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
      0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
   };
   PIXELFORMATDESCRIPTOR pfd;
   memcpy(&pfd, init, sizeof pfd);