First version, converts files and displays some info.

Program.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.IO;
+
+namespace MysteryGiftConvert {
+	class Program {
+		static void Main( string[] args ) {
+			if ( args.Length < 1 ) {
+				Console.WriteLine( "Usage: MysteryGiftConvert infile.pcd [outfile.myg]" );
+				return;
+			}
+
+			string inFilename = args[0];
+			var file = File.ReadAllBytes( inFilename );
+
+			if ( file.Length != 856 ) {
+				Console.WriteLine( "Input is not a Generation 4 pcd file!" );
+				return;
+			}
+
+			// display some info about the wonder card
+			ushort cardId = BitConverter.ToUInt16( file, 0x150 );
+			Console.WriteLine( "Card ID: " + cardId );
+
+			string outFilename = args.Length >= 2 ? args[1] : cardId + ".myg";
+
+			ushort gameBitmask = BitConverter.ToUInt16( file, 0x14C );
+			Console.Write( "This Mystery Gift is valid for:" );
+			if ( ( gameBitmask & 0x0400 ) == 0x0400 ) { Console.Write( " Diamond" ); }
+			if ( ( gameBitmask & 0x0800 ) == 0x0800 ) { Console.Write( " Pearl" ); }
+			if ( ( gameBitmask & 0x1000 ) == 0x1000 ) { Console.Write( " Platinum" ); }
+			if ( ( gameBitmask & 0x0080 ) == 0x0080 ) { Console.Write( " HeartGold" ); }
+			if ( ( gameBitmask & 0x0100 ) == 0x0100 ) { Console.Write( " SoulSilver" ); }
+			Console.WriteLine();
+
+			// to convert a pcd into a wifi-distributable wonder card file, copy the short description and "header" data from 0x104 to 0x154 to the start of the file
+			var outStream = new FileStream( outFilename, FileMode.Create );
+
+			outStream.Write( file, 0x104, 0x50 );
+			outStream.Write( file, 0, file.Length );
+
+			outStream.Close();
+
+			Console.WriteLine( "Converted " + Path.GetFileName( inFilename ) + " to " + Path.GetFileName( outFilename ) + "!" );
+		}
+	}
+}