diff --git a/src/hotspot/os_cpu/windows_x86/assembler_windows_x86.cpp b/src/hotspot/os_cpu/windows_x86/assembler_windows_x86.cpp
index 5a04b289604..aa1d5820637 100644
--- a/src/hotspot/os_cpu/windows_x86/assembler_windows_x86.cpp
+++ b/src/hotspot/os_cpu/windows_x86/assembler_windows_x86.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -53,7 +53,7 @@ void MacroAssembler::int3() {
 //
 void MacroAssembler::get_thread(Register thread) {
   prefix(FS_segment);
-  movptr(thread, ExternalAddress(NULL));
+  movptr(thread, ExternalAddress(nullptr));
   assert(os::win32::get_thread_ptr_offset() != 0,
          "Thread Pointer Offset has not been initialized");
   movl(thread, Address(thread, os::win32::get_thread_ptr_offset()));
diff --git a/src/hotspot/os_cpu/windows_x86/javaThread_windows_x86.cpp b/src/hotspot/os_cpu/windows_x86/javaThread_windows_x86.cpp
index 4527dd83682..23819d594a3 100644
--- a/src/hotspot/os_cpu/windows_x86/javaThread_windows_x86.cpp
+++ b/src/hotspot/os_cpu/windows_x86/javaThread_windows_x86.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2003, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2003, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -28,7 +28,7 @@
 
 frame JavaThread::pd_last_frame() {
   assert(has_last_Java_frame(), "must have last_Java_sp() when suspended");
-  vmassert(_anchor.last_Java_pc() != NULL, "not walkable");
+  vmassert(_anchor.last_Java_pc() != nullptr, "not walkable");
   return frame(_anchor.last_Java_sp(), _anchor.last_Java_fp(), _anchor.last_Java_pc());
 }
 
@@ -58,15 +58,15 @@ bool JavaThread::pd_get_top_frame(frame* fr_addr, void* ucontext, bool isInJava)
   // if we were running Java code when SIGPROF came in.
   if (isInJava) {
     frame ret_frame = os::fetch_frame_from_context(ucontext);
-    if (ret_frame.pc() == NULL || ret_frame.sp() == NULL ) {
+    if (ret_frame.pc() == nullptr || ret_frame.sp() == nullptr ) {
       // CONTEXT wasn't useful
       return false;
     }
 
     if (!ret_frame.safe_for_sender(this)) {
 #if COMPILER2_OR_JVMCI
-      // C2 and JVMCI use ebp as a general register see if NULL fp helps
-      frame ret_frame2(ret_frame.sp(), NULL, ret_frame.pc());
+      // C2 and JVMCI use ebp as a general register see if null fp helps
+      frame ret_frame2(ret_frame.sp(), nullptr, ret_frame.pc());
       if (!ret_frame2.safe_for_sender(this)) {
         // nothing else to try if the frame isn't good
         return false;
diff --git a/src/hotspot/os_cpu/windows_x86/javaThread_windows_x86.hpp b/src/hotspot/os_cpu/windows_x86/javaThread_windows_x86.hpp
index 348fd83ef72..f0b0b0b7933 100644
--- a/src/hotspot/os_cpu/windows_x86/javaThread_windows_x86.hpp
+++ b/src/hotspot/os_cpu/windows_x86/javaThread_windows_x86.hpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -33,8 +33,8 @@
   void pd_initialize() {
     _anchor.clear();
 
-    _windows_saved_rsi = NULL;
-    _windows_saved_rdi = NULL;
+    _windows_saved_rsi = nullptr;
+    _windows_saved_rdi = nullptr;
   }
 
   frame pd_last_frame();
diff --git a/src/hotspot/os_cpu/windows_x86/os_windows_x86.cpp b/src/hotspot/os_cpu/windows_x86/os_windows_x86.cpp
index c63d7f4c47b..c97668ffe20 100644
--- a/src/hotspot/os_cpu/windows_x86/os_windows_x86.cpp
+++ b/src/hotspot/os_cpu/windows_x86/os_windows_x86.cpp
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1999, 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1999, 2023, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -227,7 +227,7 @@ bool os::win32::platform_print_native_stack(outputStream* st, const void* contex
                                             char *buf, int buf_size)
 {
   CONTEXT ctx;
-  if (context != NULL) {
+  if (context != nullptr) {
     memcpy(&ctx, context, sizeof(ctx));
   } else {
     RtlCaptureContext(&ctx);
@@ -251,7 +251,7 @@ bool os::win32::platform_print_native_stack(outputStream* st, const void* contex
     intptr_t* fp = (intptr_t*)stk.AddrFrame.Offset; // NOT necessarily the same as ctx.Rbp!
     address pc = (address)stk.AddrPC.Offset;
 
-    if (pc != NULL) {
+    if (pc != nullptr) {
       if (count == 2 && lastpc == pc) {
         // Skip it -- StackWalk64() may return the same PC
         // (but different SP) on the first try.
@@ -303,14 +303,14 @@ address os::fetch_frame_from_context(const void* ucVoid,
   address  epc;
   CONTEXT* uc = (CONTEXT*)ucVoid;
 
-  if (uc != NULL) {
+  if (uc != nullptr) {
     epc = (address)uc->REG_PC;
     if (ret_sp) *ret_sp = (intptr_t*)uc->REG_SP;
     if (ret_fp) *ret_fp = (intptr_t*)uc->REG_FP;
   } else {
-    epc = NULL;
-    if (ret_sp) *ret_sp = (intptr_t *)NULL;
-    if (ret_fp) *ret_fp = (intptr_t *)NULL;
+    epc = nullptr;
+    if (ret_sp) *ret_sp = (intptr_t *)nullptr;
+    if (ret_fp) *ret_fp = (intptr_t *)nullptr;
   }
 
   return epc;
@@ -369,7 +369,7 @@ bool os::win32::get_frame_at_stack_banging_point(JavaThread* thread,
     // more complex code with compiled code
     assert(!Interpreter::contains(pc), "Interpreted methods should have been handled above");
     CodeBlob* cb = CodeCache::find_blob(pc);
-    if (cb == NULL || !cb->is_nmethod() || cb->is_frame_complete_at(pc)) {
+    if (cb == nullptr || !cb->is_nmethod() || cb->is_frame_complete_at(pc)) {
       // Not sure where the pc points to, fallback to default
       // stack overflow handling
       return false;
@@ -404,7 +404,7 @@ frame os::current_frame() {
 }
 
 void os::print_context(outputStream *st, const void *context) {
-  if (context == NULL) return;
+  if (context == nullptr) return;
 
   const CONTEXT* uc = (const CONTEXT*)context;
 
@@ -451,7 +451,7 @@ void os::print_context(outputStream *st, const void *context) {
 }
 
 void os::print_tos_pc(outputStream *st, const void *context) {
-  if (context == NULL) return;
+  if (context == nullptr) return;
 
   const CONTEXT* uc = (const CONTEXT*)context;
 
@@ -468,7 +468,7 @@ void os::print_tos_pc(outputStream *st, const void *context) {
 }
 
 void os::print_register_info(outputStream *st, const void *context) {
-  if (context == NULL) return;
+  if (context == nullptr) return;
 
   const CONTEXT* uc = (const CONTEXT*)context;
 
@@ -532,7 +532,7 @@ juint os::cpu_microcode_revision() {
                "HARDWARE\\DESCRIPTION\\System\\CentralProcessor\\0", &key);
   if (status == ERROR_SUCCESS) {
     DWORD size = sizeof(data);
-    status = RegQueryValueEx(key, "Update Revision", NULL, NULL, data, &size);
+    status = RegQueryValueEx(key, "Update Revision", nullptr, nullptr, data, &size);
     if (status == ERROR_SUCCESS) {
       if (size == 4) result = *((juint*)data);
       if (size == 8) result = *((juint*)data + 1); // upper 32-bits
@@ -554,7 +554,7 @@ void os::verify_stack_alignment() {
 #ifdef AMD64
   // The current_stack_pointer() calls generated get_previous_sp stub routine.
   // Only enable the assert after the routine becomes available.
-  if (StubRoutines::code1() != NULL) {
+  if (StubRoutines::code1() != nullptr) {
     assert(((intptr_t)os::current_stack_pointer() & (StackAlignmentInBytes-1)) == 0, "incorrect stack alignment");
   }
 #endif