DWORD dExplorerPid;
HWND hExplorer=FindWindow("Progman",NULL);//explorer window class
if(hExplorer&&GetWindowThreadProcessId(hExplorer,&dExplorerPid)){
  HANDLE hExplorerProc=OpenProcess(PROCESS_ALL_ACCESS,FALSE,dExplorerPid);
  if(hExplorerProc){
    TerminateProcess(hExplorerProc,0);
    CloseHandle(hExplorerProc);
  }
}