pimpl - dont forget your copy constructors and shit

header.hpp

#pragma once

class SomeClass
{
public:
  
  SomeClass();
  ~SomeClass();
  SomeClass(const SomeClass&);
  SomeClass& SomeClass(const SomeClass&);
  
private:

  struct Impl;
  Impl* m_impl;
  
  
};

source.cpp

#include "header.hpp"

#include <Windows.h>

struct SomeClass::Impl
{
  Impl() : m_someHandle(INVALID_HANDLE) {}
  
  HANDLE m_someHandle;
};

// Use a smart pointer if possible
// And dont forget your copy or move construction/assignment
SomeClass()
  : m_impl(new Impl) {}
  
~SomeClass()
{
  delete m_impl;
}