basic window wont show on vista 64

ive just switched from xp 32bit to vista 64bit and installed visual studio express 2008 , the code compiles fine but fails to show the window , but the process is running in task manager , anyone know the problem

Code:

#include "stdafx.h"
#include <windows.h>
#include "Dx.h"



HWND g_hwnd;

INT WINAPI WinMain(HINSTANCE hInstance,HINSTANCE,LPSTR,INT)
{
	RegisterWindowClass(hInstance);
	RegisterWindow(hInstance);
	ShowWindow(g_hwnd,SW_SHOWDEFAULT);
	UpdateWindow(g_hwnd);
	INT result = StartMessageLoop();
	return result;
}

LRESULT WINAPI WndProc(HWND hWnd,UINT msg,WPARAM wParam,LPARAM lParam)
{
	switch(msg)
	{
	case WM_CREATE:
		return 0;

	case WM_DESTROY:
		PostQuitMessage(0);
		return 0;

	case WM_PAINT:
		ValidateRect(g_hwnd,NULL);
		return 0;
	}
	return DefWindowProc(hWnd,msg,wParam,lParam);
}

void RegisterWindowClass(HINSTANCE hInstance)
{
	WNDCLASSEX wc;
	wc.cbSize = sizeof(WNDCLASSEX);
	wc.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC;
	wc.lpfnWndProc = WndProc;
	wc.cbClsExtra = 0;
	wc.cbWndExtra = 0;
	wc.hInstance = hInstance;
	wc.hIcon = LoadIcon(NULL,IDI_APPLICATION);
	wc.hCursor = (HCURSOR)LoadCursor(hInstance,IDC_ARROW);
	wc.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
	wc.lpszMenuName = NULL;
	wc.lpszClassName = "WinApp";
	wc.hIconSm = NULL;
	RegisterClassEx(&wc);
}

void RegisterWindow(HINSTANCE hInstance)
{
	g_hwnd = CreateWindowEx(NULL,"WinApp","Basic Windows Application",
		                        WS_OVERLAPPEDWINDOW,
								100,
								100,
								648,
								514,
								GetDesktopWindow(),
                                NULL,
								hInstance,
								NULL);
}

WPARAM StartMessageLoop()
{
	MSG msg;
	while(1)
	{
		if(PeekMessage(&msg,NULL,0,0,PM_REMOVE))
		{
			if(msg.message == WM_QUIT)
				break;
			TranslateMessage(&msg);
			DispatchMessage(&msg);
		}
		else
		{

		}
	}
	return msg.wParam;
}

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Code:

WNDCLASSEX wc = { 0 };