제가 만들어 놓은 프로그램입니다...윈도우.OS별로 재부팅 및 파워 OFF 다..됩니다..
호출하실때 iFlag 값은 EWX_POWEROFF, EWX_REBOOT

#include <shellapi.h>

//---------------------------------------------------------------------------
void __fastcall ShutDown(int iFlag)
{
    //0: default 1: 3.1// 2: 98  //3: 95 //4: NT
    OSVERSIONINFO verInfo;
    verInfo.dwOSVersionInfoSize = sizeof(verInfo);
    GetVersionEx(&verInfo) ;

    switch(verInfo.dwPlatformId)
    {
        case VER_PLATFORM_WIN32_WINDOWS:
            if(iFlag == EWX_POWEROFF) iFlag = EWX_SHUTDOWN;   
            ExitWindowsEx(EWX_FORCE|iFlag,0);
            break;
        case VER_PLATFORM_WIN32_NT:
        default:
            HANDLE hToken;
            TOKEN_PRIVILEGES tkp;

            if(!OpenProcessToken(GetCurrentProcess(), TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY, &hToken))
            {
                Application->MessageBox("OpenProcessToken failed.",
                                        "Message",
                                        MB_ICONINFORMATION|MB_OK);
            }

            LookupPrivilegeValue( NULL, SE_SHUTDOWN_NAME, &tkp.Privileges[0].Luid);

            tkp.PrivilegeCount = 1;
            tkp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;

            AdjustTokenPrivileges( hToken, FALSE, &tkp,    0, (PTOKEN_PRIVILEGES) NULL, 0);

            if (GetLastError() != ERROR_SUCCESS)
            {
                Application->MessageBox("AdjustTokenPrivileges enable failed.",
                                        "Message",
                                        MB_ICONINFORMATION|MB_OK);
            }

            ExitWindowsEx(EWX_FORCE|iFlag,1);
            break;
    }
}