diff --git a/TODO b/TODO
index 2e499306..df9cbf6f 100644
--- a/TODO
+++ b/TODO
@@ -2,7 +2,6 @@ Windows Port TODO
 -----------------
 
 - Check WITH_SYSTEMWIDE
-- Ensure that all new headers have header guards.
 - Replace atoi(), atol() and atof() in Windows code.
 - Replace rand() with randk() in Windows code.
 - Implement Sys_AppActivate() as soon as cl_hwnd is
diff --git a/src/windows/header/conproc.h b/src/windows/header/conproc.h
index 011347de..2a4ffd1d 100644
--- a/src/windows/header/conproc.h
+++ b/src/windows/header/conproc.h
@@ -24,6 +24,11 @@
  * =======================================================================
  */
 
+#ifndef WIN_CONPROC_H
+#define WIN_CONPROC_H
+
 void InitConProc(int argc, char **argv);
 void DeinitConProc(void);
 
+#endif
+
diff --git a/src/windows/header/glwindow.h b/src/windows/header/glwindow.h
index 4a34b78d..d7947fac 100644
--- a/src/windows/header/glwindow.h
+++ b/src/windows/header/glwindow.h
@@ -24,8 +24,8 @@
  * =======================================================================
  */ 
 
-#ifndef __GLW_WIN_H__
-#define __GLW_WIN_H__
+#ifndef WIN_GLW_WIN_H__
+#define WIN_GLW_WIN_H__
 
 typedef struct
 {
diff --git a/src/windows/header/qal.h b/src/windows/header/qal.h
index 5ab765ec..5b09823b 100644
--- a/src/windows/header/qal.h
+++ b/src/windows/header/qal.h
@@ -28,8 +28,8 @@
 
 #ifdef USE_OPENAL
 
-#ifndef _QAL_API_H_
-#define _QAL_API_H_
+#ifndef WIN_QAL_API_H_
+#define WIN_QAL_API_H_
 
 #include <AL/al.h>
 #include <AL/efx.h>
@@ -132,5 +132,5 @@ qboolean QAL_Init(void);
  */
 void QAL_Shutdown(void);
 
-#endif /* _QAL_API_H_ */
+#endif /* WIN_QAL_API_H_ */
 #endif /* USE_OPENAL */
diff --git a/src/windows/header/resource.h b/src/windows/header/resource.h
index dfd82ef6..bc6bfad3 100644
--- a/src/windows/header/resource.h
+++ b/src/windows/header/resource.h
@@ -1,3 +1,5 @@
+#ifndef WIN_RESOURCE_H
+#define WIN_RESOURCE_H
 #define IDI_ICON1                       101
 
 #ifdef APSTUDIO_INVOKED
@@ -9,3 +11,5 @@
 #endif
 #endif
 
+#endif
+
diff --git a/src/windows/header/winquake.h b/src/windows/header/winquake.h
index 9bcb3250..438b9c0c 100644
--- a/src/windows/header/winquake.h
+++ b/src/windows/header/winquake.h
@@ -24,6 +24,9 @@
  * =======================================================================
  */ 
 
+#ifndef WIN_WINQUAKE_H
+#define WIN_WINQUAKE_H
+
 #include <windows.h>
 
 #define WINDOW_STYLE (WS_OVERLAPPED | WS_BORDER | WS_CAPTION | WS_VISIBLE)
@@ -62,3 +65,5 @@ typedef struct in_state
 	int *in_speed_state;
 } in_state_t;
 
+#endif
+