Adding proper Disc identification for ISO9660 / Joliet (default target DOS)

src/BizHawk.Client.Common/RomLoader.cs

@@ -297,6 +297,9 @@ namespace BizHawk.Client.Common
 				case DiscType.Wii:
 					NoCoreForSystem(VSystemID.Raw.Wii);
 					break;
+				case DiscType.DOS:
+					game.System = VSystemID.Raw.DOS;
+					break;
 
 				case DiscType.AudioDisc:
 				case DiscType.UnknownCDFS:

src/BizHawk.Emulation.DiscSystem/DiscIdentifier.cs

@@ -112,6 +112,11 @@ namespace BizHawk.Emulation.DiscSystem
 		/// Atari Jaguar CD
 		/// </summary>
 		JaguarCD,
+
+		/// <summary>
+		/// DOS / Windows
+		/// </summary>
+		DOS,
 	}
 
 	public class DiscIdentifier
@@ -243,6 +248,10 @@ namespace BizHawk.Emulation.DiscSystem
 					return DiscType.Amiga;
 				}
 
+				// Detects ISO9660 / Joliet CD formats (target for DOS / Windows)
+				if (DetectISO9660())
+					return DiscType.DOS;
+
 				// NeoGeoCD Check
 				var absTxt = iso.Root.Children.Where(kvp => kvp.Key.Contains("ABS.TXT")).Select(kvp => kvp.Value).FirstOrDefault();
 				if (absTxt != null && SectorContains("abstracted by snk", Convert.ToInt32(absTxt.Offset))) return DiscType.NeoGeoCD;
@@ -394,6 +403,12 @@ namespace BizHawk.Emulation.DiscSystem
 			return hexString == "5D1C9EA3";
 		}
 
+		private bool DetectISO9660()
+		{
+			return StringAt("CD001", 1, 16);
+		}
+
+
 		private bool DetectJaguarCD()
 		{
 			// Atari Jaguar CDs are multisession discs which are encoded like audio CDs