Win32 problems...

Hey. Something strange is going on with my window; if I use the menu at all and select any options and then close it down I can't recompile the code after changes as it says the exe is still in use, and it is when I look at task manager which forces me to destroy the window from in there...obviously not good. I've searched over MSDN pages and googled everything I can think of, but still no luck... Heres the code anyway; there is a fair amount so I appreciate any replies from anyone. Thanks.

#include "WinMain.h"
#include "GameWorld.h"
#include "resource.h"

//--------------------------------------------------------------------------------------------------
/**
@globals
**/
//--------------------------------------------------------------------------------------------------
bool       g_Exiting      = false;

int        g_WindowWidth  = 1024;   // Defaulted window width
int        g_WindowHeight = 768;    // Defaulted window height

int        g_Fullscreen   = 0;      // Defaulted to not full screen

f64	   g_FOV          = 45.0;   // Default field of view 
f64	   g_zNear        = 0.1;    // Defaulted z near plane
f64	   g_zFar         = 8000.0; // Defaulted z far plane

HDC	   g_HDC          = NULL;

bool	   g_ShowFPS	  = false;

Timer      g_Timer;
GameWorld* g_pGameWorld	  = NULL;


//--------------------------------------------------------------------------------------------------
/**
@function		SetupPixelFormat
@brief			Create the rendering context
**/
//--------------------------------------------------------------------------------------------------
void SetupPixelFormat( HDC hDC )
{
	PIXELFORMATDESCRIPTOR pfd =
	{	
		sizeof( PIXELFORMATDESCRIPTOR ), // size
		1,							     // version
		PFD_SUPPORT_OPENGL |		     // OpenGL window
		PFD_DRAW_TO_WINDOW |		     // render to window
		PFD_DOUBLEBUFFER,			     // support double-buffering
		PFD_TYPE_RGBA,				     // color type
		32,								 // preferred color depth
		0, 0, 0, 0, 0, 0,			     // color bits (ignored)
		0,							     // no alpha buffer
		0,							     // alpha bits (ignored)
		0,							     // 0
		0, 0, 0, 0,					     // accumulation bits (ignored)
		24,							     // depth buffer
		0,							     // stencil buffer
		0,							     // no auxiliary buffers
		PFD_MAIN_PLANE,				     // main layer
		0,							     // reserved
		0, 0, 0,					     // no layer, visible, damage masks
	};

	int pixelFormat = ChoosePixelFormat( hDC, &pfd );

	SetPixelFormat( hDC, pixelFormat, &pfd );
}

//--------------------------------------------------------------------------------------------------
/**
@function		MainWindowProc
@brief			Windows callback function
**/
//--------------------------------------------------------------------------------------------------
LRESULT CALLBACK MainWindowProc( HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam )
{
	static HDC hDC;
	static HGLRC hRC;

	static int height = 0;
	static int width  = 0;

	// Get a pointer to the camera each time the callback is invoked...
	Camera* pCamera = NULL;

	// Retrieve a pointer to the game world if it has been created...
	if( g_pGameWorld )
		pCamera = g_pGameWorld->GetCamera();

	// Get the window handle for the mouse each time the call back function is invoked
	if( pCamera )	
		pCamera->GetWindowHandle( hWnd );

	// dispatch messages
	switch( uMsg )
	{	

	// Process Menu commands
	case WM_COMMAND:
			
		if( LOWORD( wParam ) == ID_FILE_QUIT )
			SendMessage( hWnd, WM_CLOSE, 0, 0 );

		if( LOWORD( wParam ) == ID_TERRAIN_WIREFRAMEON )
			g_pGameWorld->GetTerrain()->ToggleRenderMode();

		if( LOWORD( wParam ) == ID_FILE_SHOWFPSON )
			g_ShowFPS = !g_ShowFPS;

		break;

	case WM_CREATE:			// window creation
		hDC = GetDC( hWnd );

		SetupPixelFormat( hDC );

		hRC = wglCreateContext( hDC );

		wglMakeCurrent( hDC, hRC );

		break;

	case WM_DESTROY:				// window destroy

	case WM_QUIT:

	case WM_CLOSE:					// windows is closing

		// De-select rendering context and delete it
		wglMakeCurrent( NULL, NULL );

		wglDeleteContext( hRC );
 
		ReleaseDC( hWnd, g_HDC );

		break;

	case WM_SIZE:
		height = HIWORD( lParam );		// retrieve width and height
		width  = LOWORD( lParam );

		if( height == 0 )
			height = 1;

		// Get the dimensions of the screen
		if( pCamera )	
			pCamera->GetWindowDimensions( width, height );

		// Size the OpenGL view port
		glViewport( 0, 0, width, height );

		glMatrixMode( GL_PROJECTION );
		glLoadIdentity();

		// Calculate OpenGL perspective
		gluPerspective( g_FOV, g_WindowWidth/g_WindowHeight, g_zNear, g_zFar );

		glMatrixMode( GL_MODELVIEW );
		glLoadIdentity();

		break;


	case WM_ACTIVATEAPP:		// activate app
		break;

	case WM_PAINT:				// paint
		PAINTSTRUCT ps;

		BeginPaint( hWnd, &ps );

		EndPaint( hWnd, &ps );

		break;

	case WM_LBUTTONDOWN:

		if( pCamera )	
			pCamera->SetViewWithMouse( true );
				
		ShowCursor( false );

		break;

	case WM_RBUTTONDOWN:
		break;

	case WM_MOUSEMOVE:
		break;

	case WM_LBUTTONUP:

		if( pCamera )
			pCamera->SetViewWithMouse( false );

			ShowCursor( true );
			
		break;

	case WM_RBUTTONUP:
		break;

	case WM_KEYUP:
		break;

	case WM_KEYDOWN:
		int fwKeys;
		LPARAM keyData;
		fwKeys = (int)wParam;      // virtual-key code 
		keyData = lParam;          // key data 

		switch( fwKeys )
		{

		case VK_ESCAPE:
			PostQuitMessage(0);

			break;

		default:
			break;
		}

		break;

	default:
		break;
	}

	return DefWindowProc( hWnd, uMsg, wParam, lParam );
}

//--------------------------------------------------------------------------------------------------
/**
@function		WinMain
@brief			Windows main function
**/
//--------------------------------------------------------------------------------------------------
int WINAPI WinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd )
{
	// Load the window data	
	LoadWindowData();

	WNDCLASSEX windowClass;		// window class
	HWND	   hwnd;			// window handle
	MSG		   msg;				// message
	DWORD	   dwExstyle;		// Window Extended style
	DWORD	   dwstyle;			// Window style
	RECT	   windowRect;

	windowRect.left   =(long)0;						// Set Left Value To 0
	windowRect.right  =(long)g_WindowWidth;			// Set Right Value To Requested Width
	windowRect.top    =(long)0;						// Set Top Value To 0
	windowRect.bottom =(long)g_WindowHeight;		// Set Bottom Value To Requested Height

	// fill out the window class structure
	windowClass.cbSize			= sizeof( WNDCLASSEX );
	windowClass.style			= CS_HREDRAW | CS_VREDRAW;
	windowClass.lpfnWndProc		= MainWindowProc;
	windowClass.cbClsExtra		= 0;
	windowClass.cbWndExtra		= 0;
	windowClass.hInstance		= hInstance;
	windowClass.hIcon			= LoadIcon( NULL, IDI_APPLICATION );	// default icon
	windowClass.hIconSm			= NULL;
	windowClass.hCursor			= LoadCursor( NULL, IDC_ARROW );		// default arrow
	windowClass.hbrBackground	= NULL;									// don't need background
	windowClass.lpszClassName	= kAppName;


	// Menu item
	windowClass.lpszMenuName    = MAKEINTRESOURCE( IDR_MENU1 );


	//windowClass.hIcon           = LoadIcon( GetModuleHandle( NULL ), MAKEINTRESOURCE( IDI_ICON1 ) );

	//windowClass.hIconSm         = ( HICON )LoadImage( GetModuleHandle( NULL ), MAKEINTRESOURCE( IDI_ICON1 ), IMAGE_ICON, 32, 32, 0 );


	// Register the windows class
	if ( !RegisterClassEx( &windowClass ) )
	{
		MessageBox( NULL, "WinMain: Failed to register class!", NULL, MB_OK );

		return 0;
	}


	if ( g_Fullscreen )								// full screen?
	{
		DEVMODE dmScreenSettings;					// device mode

		memset( &dmScreenSettings, 0, sizeof( dmScreenSettings ) );

		dmScreenSettings.dmSize       = sizeof(dmScreenSettings);	
		dmScreenSettings.dmPelsWidth  = g_WindowWidth;								  // screen width
		dmScreenSettings.dmPelsHeight = g_WindowHeight;								  // screen height
		dmScreenSettings.dmBitsPerPel = kWindowBits;								  // bits per pixel
		dmScreenSettings.dmFields     = DM_BITSPERPEL | DM_PELSWIDTH | DM_PELSHEIGHT;

		if( ChangeDisplaySettings( &dmScreenSettings, CDS_FULLSCREEN ) != DISP_CHANGE_SUCCESSFUL )
		{
			// Setting display mode failed, switch to windowed
			MessageBox( NULL, "WinMain: Display mode failed!", NULL, MB_OK );

			g_Fullscreen = 0;
		}
	}

	if( g_Fullscreen )								
	{
		dwExstyle = WS_EX_APPWINDOW;				// Window Extended style
		dwstyle   = WS_POPUP;						// Windows style
	}
	else
	{
		dwExstyle = WS_EX_APPWINDOW | WS_EX_WINDOWEDGE;		// Window Extended style
		dwstyle   = WS_OVERLAPPEDWINDOW;					// Windows style
	}

	AdjustWindowRectEx( &windowRect, dwstyle, false, dwExstyle );		// Adjust Window To True Requested Size

	// class registered, so now create our window
	hwnd = CreateWindowEx( NULL,								// extended style
						   kAppName,							// class name
						   kAppName,							// app name
						   dwstyle | WS_CLIPCHILDREN |
						   WS_CLIPSIBLINGS,
						   0, 0,								// x,y coordinate
						   windowRect.right - windowRect.left,
						   windowRect.bottom - windowRect.top,  // width, height
						   NULL,								// handle to parent
						   NULL,								// handle to menu
						   hInstance,							// application instance
						   NULL );								// no extra params

	g_HDC = GetDC( hwnd );


	// Check if window creation failed (hwnd would equal NULL)
	if( !hwnd )
		return 0;

	ShowWindow( hwnd, SW_SHOW );			// display the window
	UpdateWindow( hwnd );					// update the window


        if( !Timer::QueryHighPerformanceTimer() )
	{
		MessageBox( NULL, "WinMain: QueryHighPerformanceTimer failed!", NULL, MB_OK );

		return 0;
	}

	
	g_Timer.Initialise();

	g_pGameWorld = new GameWorld();

	if( !g_pGameWorld->Initialise( hwnd ) )
	{
		MessageBox( NULL, "WinMain: Failed to initialise GameWorld!", NULL, MB_OK );

		delete g_pGameWorld;

		_CrtDumpMemoryLeaks();

		return 0;
	}	

	glEnable( GL_TEXTURE_2D );
	glEnable( GL_DEPTH_TEST );
	glEnable( GL_BLEND );
	glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );


	while( !g_Exiting )
	{
		g_Timer.Update();
		f32 delta = g_Timer.GetDeltaTime();

		g_pGameWorld->Update( delta );
		g_pGameWorld->Render();

		SwapBuffers( g_HDC );

		if( g_ShowFPS )
			CalculateFrameRate( hwnd );
		else
			SetWindowText( hwnd, kAppName );

		while( PeekMessage( &msg, NULL, 0, 0, PM_NOREMOVE ) )
		{
			if( !GetMessage( &msg, NULL, 0, 0 ) )
			{
				g_Exiting = true;

				break;
			}

			TranslateMessage( &msg );
			DispatchMessage( &msg );
		}
	}


	g_pGameWorld->Shutdown();
	delete g_pGameWorld;
	g_pGameWorld = NULL;

	// Test for CRT leaks...
	_CrtDumpMemoryLeaks();

	if( !DestroyWindow( hwnd ) )
		MessageBox( NULL, "WinMain: Failed to destroy window!", NULL, MB_OK );


	// Unregister the class
	if( !UnregisterClass( kAppName, windowClass.hInstance ) )
		MessageBox( NULL, "WinMain: Failed to unregister class!", NULL, MB_OK );


	return (int)msg.wParam;
}