帮忙看看有没有错误。

为什么生成的DLL不能注册，要怎样将它注入到指定进程？ 下面是代码。#include <windows.h>#include "stdafx.h"WNDPROC lpOldWndFunc=NULL;LRESULT CALLBACK WinProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
switch(uMsg)
{
case WM_SYSCOMMAND:
 switch(LOWORD(wParam))
{
case 988:
MessageBox(hwnd,"test","About this demo...",MB_OK);
return TRUE;
}
break;}
return CallWindowProc(lpOldWndFunc,hwnd,uMsg,wParam,lParam);
}
BOOL CALLBACK EnumWinProc(HWND hwnd, LPARAM lParam)
{
DWORD PID;
GetWindowThreadProcessId(hwnd,&PID);
if(PID==(DWORD)lParam)
{
    HMENU SysMenu=GetSystemMenu(hwnd,FALSE);
    if(SysMenu)
    {
        int ItemCount=GetMenuItemCount(SysMenu);
        InsertMenu(SysMenu,ItemCount-1,MF_BYPOSITION|MF_STRING,988,"About This Demo...");
        lpOldWndFunc=(WNDPROC)GetWindowLong(hwnd,GWL_WNDPROC);
        SetWindowLong(hwnd,GWL_WNDPROC,(LONG)WinProc);    }}
return TRUE;
}
BOOL APIENTRY DllMain( HANDLE hModule, 
DWORD ul_reason_for_call, 
LPVOID lpReserved
                    )
{
    switch(ul_reason_for_call)
    {
    case DLL_PROCESS_ATTACH:
        EnumWindows(EnumWinProc,(LPARAM)(GetCurrentProcessId()));
        break;
    }return TRUE;
}