Probleme mit NetRemoteComputerSupports

[Luckie]

Ich versuche gerade die Funktion NetRemoteComputerSupports zu benutzen. Bishert habe ich das so:

Delphi-Quellcode:

const
  SUPPORTS_REMOTE_ADMIN_PROTOCOL = $00000002;
  SUPPORTS_RPC = $00000004;
  SUPPORTS_SAM_PROTOCOL = $00000008;
  SUPPORTS_UNICODE = $00000010;
  SUPPORTS_LOCAL = $00000020;
  SUPPORTS_ANY = $FFFFFFFF;

  NERR_Success = 0;

function NetRemoteComputerSupports(UNCServername: PWideChar; OptionswWanted:
  DWORD; var OptionSupported: DWORD): NET_API_STATUS; external 'netapi32.dll'
  Name 'NetRemoteComputerSupports';

function NetApiBufferFree(Buffer: Pointer): NET_API_STATUS; stdcall;
  external 'netapi32.dll' Name 'NetApiBufferFree';

implementation

{$R *.dfm}


procedure TForm1.btnGetClick(Sender: TObject);
var
  OptionsSupported: DWORD;
  ret: NET_API_STATUS;
begin
  ret := NetRemoteComputerSupports(PWideChar(WideString(edtComputer.Text)),
    SUPPORTS_ANY, OptionsSupported);
  if ret = NERR_Success then
  begin
    CheckBox1.Checked := (OptionsSupported and SUPPORTS_REMOTE_ADMIN_PROTOCOL)
      = 0;
  end;
end;

Aber ret ist 123, was auch immer das bedeuted, und ich bekomme dann eine AccessViolation. Ich sehe aber meinen Fehler nicht.