add GetMachineId

stepmania/src/arch/ArchHooks/ArchHooks.h

@@ -24,6 +24,11 @@ public:
 	 */
 	static RString GetPreferredLanguage();
 
+	/*
+	 * A string that uniquely identifies the machine in some way
+	 */
+	virtual RString GetMachineId() { return RString(); }
+
 	/*
 	 * If this is a second instance, return true.  Optionally, give focus to the existing
 	 * window.

stepmania/src/arch/ArchHooks/ArchHooks_Win32.cpp

@@ -9,6 +9,7 @@
 #include "archutils/win32/DebugInfoHunt.h"
 #include "archutils/win32/RestartProgram.h"
 #include "archutils/win32/GotoURL.h"
+#include "archutils/Win32/RegistryAccess.h"
 
 static HANDLE g_hInstanceMutex;
 static bool g_bIsMultipleInstance = false;
@@ -72,6 +73,16 @@ static BOOL CALLBACK GetEnabledPopup( HWND hWnd, LPARAM lParam )
 	return FALSE;
 }
 
+static const RString CURRENT_VERSION_KEY = "HKEY_LOCAL_MACHINE\\Software\\Microsoft\\Windows\\CurrentVersion";
+
+RString ArchHooks_Win32::GetMachineId()
+{
+	RString s;
+	if( RegistryAccess::GetRegValue( CURRENT_VERSION_KEY, "ProductID", s ) )
+		return s;
+	return RString();
+}
+
 bool ArchHooks_Win32::CheckForMultipleInstances()
 {
 	if( !g_bIsMultipleInstance )

stepmania/src/arch/ArchHooks/ArchHooks_Win32.h

@@ -12,6 +12,7 @@ public:
 	RString GetArchName() { return "Windows"; }
 	void DumpDebugInfo();
 	void RestartProgram();
+	RString GetMachineId();
 	bool CheckForMultipleInstances();
 
 	int OldThreadPriority;