diff --git a/reactos/drivers/ksfilter/ks/ks.rbuild b/reactos/drivers/ksfilter/ks/ks.rbuild
index 96fd55cc985..8862684d5df 100644
--- a/reactos/drivers/ksfilter/ks/ks.rbuild
+++ b/reactos/drivers/ksfilter/ks/ks.rbuild
@@ -8,7 +8,6 @@
 	<library>ntoskrnl</library>
 	<library>hal</library>
 	<define name="BUILDING_KS" />
-	<define name="_NTDDK_" />
 	<define name="_COMDDK_" />
 	<file>ks.rc</file>
 	<file>allocators.c</file>
diff --git a/reactos/drivers/wdm/audio/backpln/portcls/portcls.rbuild b/reactos/drivers/wdm/audio/backpln/portcls/portcls.rbuild
index 3cacfe0906f..b82373cb20f 100644
--- a/reactos/drivers/wdm/audio/backpln/portcls/portcls.rbuild
+++ b/reactos/drivers/wdm/audio/backpln/portcls/portcls.rbuild
@@ -2,7 +2,6 @@
 <!DOCTYPE module SYSTEM "../../../../../tools/rbuild/project.dtd">
 <module name="portcls" type="kernelmodedriver" installbase="system32/drivers" installname="portcls.sys" entrypoint="0">
 	<importlibrary definition="portcls.spec" />
-	<define name="_NTDDK_" />
 	<define name="PC_NO_IMPORTS" />
 	<include base="portcls">../include</include>
 	<library>ntoskrnl</library>
diff --git a/reactos/drivers/wdm/audio/legacy/wdmaud/wdmaud.h b/reactos/drivers/wdm/audio/legacy/wdmaud/wdmaud.h
index 09cb85698f3..2e2e351b271 100644
--- a/reactos/drivers/wdm/audio/legacy/wdmaud/wdmaud.h
+++ b/reactos/drivers/wdm/audio/legacy/wdmaud/wdmaud.h
@@ -1,7 +1,6 @@
 #ifndef WDMAUD_H__
 #define WDMAUD_H__
 
-#define _NTDDK_
 #include <ntddk.h>
 #include <portcls.h>
 #define YDEBUG
diff --git a/reactos/drivers/wdm/audio/sysaudio/sysaudio.rbuild b/reactos/drivers/wdm/audio/sysaudio/sysaudio.rbuild
index 8319b928c4b..0e277357725 100644
--- a/reactos/drivers/wdm/audio/sysaudio/sysaudio.rbuild
+++ b/reactos/drivers/wdm/audio/sysaudio/sysaudio.rbuild
@@ -4,7 +4,6 @@
 	<include base="sysaudio">.</include>
 	<library>ntoskrnl</library>
 	<library>ks</library>
-	<define name="_NTDDK_" />
 	<define name="_COMDDK_" />
 	<file>main.c</file>
 	<file>sysaudio.rc</file>
diff --git a/reactos/include/ddk/ntddk.h b/reactos/include/ddk/ntddk.h
index 4f71d73c29e..ea32ed8e44d 100644
--- a/reactos/include/ddk/ntddk.h
+++ b/reactos/include/ddk/ntddk.h
@@ -24,8 +24,8 @@
  *    _X86_        - X86 environment
  */
 
-#ifndef __NTDDK_H
-#define __NTDDK_H
+#ifndef _NTDDK_
+#define _NTDDK_
 
 //
 // Dependencies
@@ -63,4 +63,4 @@ typedef GUID UUID;
 /* Definitions only in Windows NT 4 */
 #include "winnt4.h"
 
-#endif /* __NTDDK_H */
+#endif /* _NTDDK_ */
diff --git a/reactos/include/psdk/ks.h b/reactos/include/psdk/ks.h
index e8f9329506a..a1454af38a5 100644
--- a/reactos/include/psdk/ks.h
+++ b/reactos/include/psdk/ks.h
@@ -1056,7 +1056,7 @@ typedef enum
 } KSCOMPLETION_INVOCATION;
 
 
-#if defined(__NTDDK_H)
+#if defined(_NTDDK_)
 /* MOVE ME */
 typedef NTSTATUS (*PFNKSCONTEXT_DISPATCH)(
     IN PVOID Context,
@@ -1106,7 +1106,7 @@ typedef struct
     Dispatch Table
     http://www.osronline.com/DDKx/stream/ks-struct_494j.htm
 */
-#if defined(__NTDDK_H)
+#if defined(_NTDDK_)
 typedef struct
 {
     PDRIVER_DISPATCH DeviceIoControl;
@@ -1323,7 +1323,7 @@ typedef struct
 {
 } KSOBJECT_CREATE, *PKSOBJECT_CREATE;
 
-#if defined(__NTDDK_H)
+#if defined(_NTDDK_)
 typedef struct
 {
     PDRIVER_DISPATCH       Create;
@@ -1581,7 +1581,7 @@ typedef PVOID (*PFNKSINITIALIZEALLOCATOR)(
 typedef PVOID (*PFNKSDELETEALLOCATOR)(
     IN  PVOID Context);
 
-#if defined(__NTDDK_H)
+#if defined(_NTDDK_)
 typedef NTSTATUS (*PFNKSALLOCATOR)(
     IN  PIRP Irp,
     IN  ULONG BufferSize,
diff --git a/reactos/include/psdk/winnt.h b/reactos/include/psdk/winnt.h
index 729cff5ea31..5fa8c35c217 100644
--- a/reactos/include/psdk/winnt.h
+++ b/reactos/include/psdk/winnt.h
@@ -465,7 +465,7 @@ typedef DWORD FLONG;
 #define FILE_NAMED_STREAMS              0x00040000
 
 /* FIXME: Oh how I wish, I wish the w32api DDK wouldn't include winnt.h... */
-#ifndef __NTDDK_H
+#ifndef _NTDDK_
 #define IO_COMPLETION_QUERY_STATE       0x0001
 #define IO_COMPLETION_MODIFY_STATE      0x0002
 #define IO_COMPLETION_ALL_ACCESS        (STANDARD_RIGHTS_REQUIRED|SYNCHRONIZE|0x3)
@@ -480,7 +480,7 @@ typedef DWORD FLONG;
 #define MAILSLOT_NO_MESSAGE	((DWORD)-1)
 #define MAILSLOT_WAIT_FOREVER	((DWORD)-1)
 /* FIXME: Oh how I wish, I wish the w32api DDK wouldn't include winnt.h... */
-#ifndef __NTDDK_H
+#ifndef _NTDDK_
 #define PROCESS_TERMINATE	1
 #define PROCESS_CREATE_THREAD	2
 #define PROCESS_SET_SESSIONID	4
@@ -502,7 +502,7 @@ typedef DWORD FLONG;
 #define THREAD_SET_CONTEXT	16
 #define THREAD_SET_INFORMATION	32
 /* FIXME: Oh how I wish, I wish the w32api DDK wouldn't include winnt.h... */
-#ifndef __NTDDK_H
+#ifndef _NTDDK_
 #define THREAD_QUERY_INFORMATION	64
 #define THREAD_SET_THREAD_TOKEN	128
 #define THREAD_IMPERSONATE	256
@@ -510,7 +510,7 @@ typedef DWORD FLONG;
 #endif
 #define THREAD_ALL_ACCESS (STANDARD_RIGHTS_REQUIRED|SYNCHRONIZE|0x3FF)
 /* FIXME: Oh how I wish, I wish the w32api DDK wouldn't include winnt.h... */
-#ifndef __NTDDK_H
+#ifndef _NTDDK_
 #define MUTANT_QUERY_STATE	0x0001
 #define MUTANT_ALL_ACCESS	(STANDARD_RIGHTS_REQUIRED|SYNCHRONIZE|MUTANT_QUERY_STATE)
 #define TIMER_QUERY_STATE	0x0001
@@ -739,7 +739,7 @@ typedef enum {
 #define SE_REMOTE_SHUTDOWN_NAME	TEXT("SeRemoteShutdownPrivilege")
 #define SE_CREATE_GLOBAL_NAME TEXT("SeCreateGlobalPrivilege")
 /* FIXME: Oh how I wish, I wish the w32api DDK wouldn't include winnt.h... */
-#ifndef __NTDDK_H
+#ifndef _NTDDK_
 #define SE_GROUP_MANDATORY 1
 #define SE_GROUP_ENABLED_BY_DEFAULT 2
 #define SE_GROUP_ENABLED 4
@@ -1257,7 +1257,7 @@ typedef enum {
 #define MEM_PHYSICAL	   0x400000
 #define MEM_4MB_PAGES    0x80000000
 /* FIXME: Oh how I wish, I wish the w32api DDK wouldn't include winnt.h... */
-#ifndef __NTDDK_H
+#ifndef _NTDDK_
 #define MEM_IMAGE        SEC_IMAGE
 #define SEC_NO_CHANGE	0x00400000
 #define SEC_FILE	0x00800000
@@ -1274,7 +1274,7 @@ typedef enum {
 #define SECTION_MAP_EXECUTE 8
 #define SECTION_ALL_ACCESS 0xf001f
 #define WRITE_WATCH_FLAG_RESET 0x01
-#ifndef __NTDDK_H
+#ifndef _NTDDK_
 #define MESSAGE_RESOURCE_UNICODE 1
 #endif
 #define RTL_CRITSECT_TYPE 0
@@ -1900,7 +1900,7 @@ typedef struct _GENERIC_MAPPING {
 	ACCESS_MASK GenericAll;
 } GENERIC_MAPPING, *PGENERIC_MAPPING;
 /* Sigh..when will they learn... */
-#ifndef __NTDDK_H
+#ifndef _NTDDK_
 typedef struct _ACE_HEADER {
 	BYTE AceType;
 	BYTE AceFlags;
@@ -2975,7 +2975,7 @@ typedef struct _SE_IMPERSONATION_STATE {
 	SECURITY_IMPERSONATION_LEVEL Level;
 } SE_IMPERSONATION_STATE,*PSE_IMPERSONATION_STATE;
 /* Steven you are my hero when you fix the w32api ddk! */
-#if !defined(__NTDDK_H)
+#if !defined(_NTDDK_)
 typedef struct _SID_IDENTIFIER_AUTHORITY {
 	BYTE Value[6];
 } SID_IDENTIFIER_AUTHORITY,*PSID_IDENTIFIER_AUTHORITY,*LPSID_IDENTIFIER_AUTHORITY;
@@ -3175,7 +3175,7 @@ typedef struct _TAPE_CREATE_PARTITION {
 	DWORD Size;
 } TAPE_CREATE_PARTITION,*PTAPE_CREATE_PARTITION;
 /* Sigh..when will they learn... */
-#ifndef __NTDDK_H
+#ifndef _NTDDK_
 typedef struct _MEMORY_BASIC_INFORMATION {
 	PVOID BaseAddress;
 	PVOID AllocationBase;
@@ -3267,7 +3267,7 @@ RtlQueryDepthSList (
     );
 
 /* FIXME: Please oh please stop including winnt.h from the DDK... */
-#ifndef __NTDDK_H
+#ifndef _NTDDK_
 typedef struct _RTL_CRITICAL_SECTION_DEBUG {
 	WORD Type;
 	WORD CreatorBackTraceIndex;
@@ -4124,7 +4124,7 @@ typedef union _FILE_SEGMENT_ELEMENT {
 #define JOB_OBJECT_MSG_JOB_MEMORY_LIMIT       10
 
 /* FIXME: Oh how I wish, I wish the w32api DDK wouldn't include winnt.h... */
-#ifndef __NTDDK_H
+#ifndef _NTDDK_
 #define JOB_OBJECT_ASSIGN_PROCESS           1
 #define JOB_OBJECT_SET_ATTRIBUTES           2
 #define JOB_OBJECT_QUERY                    4
@@ -4184,7 +4184,7 @@ typedef struct _JOBOBJECT_BASIC_UI_RESTRICTIONS {
 	DWORD UIRestrictionsClass;
 } JOBOBJECT_BASIC_UI_RESTRICTIONS,*PJOBOBJECT_BASIC_UI_RESTRICTIONS;
 /* Steven you are my hero when you fix the w32api ddk! */
-#ifndef __NTDDK_H
+#ifndef _NTDDK_
 typedef struct _JOBOBJECT_SECURITY_LIMIT_INFORMATION {
 	DWORD SecurityLimitFlags;
 	HANDLE JobToken;
@@ -4383,7 +4383,7 @@ typedef struct _SYSTEM_BATTERY_STATE {
 	ULONG  DefaultAlert2;
 } SYSTEM_BATTERY_STATE, *PSYSTEM_BATTERY_STATE;
 
-#ifndef __NTDDK_H /* HACK!!! ntddk.h shouldn't include winnt.h! */
+#ifndef _NTDDK_ /* HACK!!! ntddk.h shouldn't include winnt.h! */
 typedef struct _PROCESSOR_POWER_INFORMATION {
 	ULONG Number;
 	ULONG MaxMhz;
@@ -4727,7 +4727,7 @@ static __inline__ PVOID GetCurrentFiber(void)
 #endif
 
 /* FIXME: Oh how I wish, I wish the w32api DDK wouldn't include winnt.h... */
-#ifndef __NTDDK_H
+#ifndef _NTDDK_
 #ifdef _M_IX86
 static __inline__ struct _TEB * NtCurrentTeb(void)
 {
diff --git a/reactos/include/reactos/debug.h b/reactos/include/reactos/debug.h
index 8e31feb9ea8..6c03d05d49b 100644
--- a/reactos/include/reactos/debug.h
+++ b/reactos/include/reactos/debug.h
@@ -17,7 +17,7 @@
 #define __INTERNAL_DEBUG
 
 /* Define DbgPrint/DbgPrintEx/RtlAssert unless the NDK is used */
-#if !defined(_RTLFUNCS_H) && (!defined(_NTDDK_) || !defined(__NTDDK_H))
+#if !defined(_RTLFUNCS_H) && !defined(_NTDDK_)
 
 /* Make sure we have basic types (some people include us *before* SDK... */
 #if !defined(_NTDEF_) && !defined(_NTDEF_H) && !defined(_WINDEF_) && !defined(_WINDEF_H)