function NetzlaufwerkVerbinden(Laufwerk: string; Pfad: string;
  Username: string; Password: string; RestoreAtLogon: Boolean): DWORD;
var
  NetResource: TNetResource;
  dwFlags: DWORD;
begin
  with NetResource do
  begin
    dwType := RESOURCETYPE_DISK;
    lpLocalName := PChar(Laufwerk);
    lpRemoteName := PChar(Pfad);
    lpProvider := nil;
  end;

  if (RestoreAtLogon) then
    dwFlags := CONNECT_UPDATE_PROFILE
  else
    dwFlags := 0;

  Result := WNetAddConnection2(NetResource, PChar(Password),
    PChar(Username), dwFlags);
end;

if (NetzlaufwerkVerbinden('X:', '\\NTSERVER\DATEN',
    'Bjoern', '', False) = 0) then
    ShowMessage('OK')
  else
    ShowMessage('Fehler!');