Проблема с потоками

#include <vcl.h>
#include <process.h>
#pragma hdrstop

#include "Unit1.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
void thr(void *Pvoid)
{
MessageBox(0,"!!!!!!","!!!!!",MB_OK);
}
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
    : TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
_beginthread(thr,0,0);
}