Get User Domain

function NetServerGetInfo (serverName : PWideChar; level : Integer;
        var bufptr : Pointer) : Cardinal; stdcall; external 'NETAPI32.DLL';
function NetApiBufferFree (buffer : Pointer) : Cardinal; stdcall; external 'NETAPI32.DLL';

type
  SERVER_INFO_503 = record
    sv503_sessopens : Integer;
    sv503_sessvcs : Integer;
    sv503_opensearch : Integer;
    sv503_sizreqbuf : Integer;
    sv503_initworkitems : Integer;
    sv503_maxworkitems : Integer;
    sv503_rawworkitems : Integer;
    sv503_irpstacksize : Integer;
    sv503_maxrawbuflen : Integer;
    sv503_sessusers : Integer;
    sv503_sessconns : Integer;
    sv503_maxpagedmemoryusage : Integer;
    sv503_maxnonpagedmemoryusage : Integer;
    sv503_enablesoftcompat :BOOL;
    sv503_enableforcedlogoff :BOOL;
    sv503_timesource :BOOL;
    sv503_acceptdownlevelapis :BOOL;
    sv503_lmannounce :BOOL;
    sv503_domain : PWideChar;
    sv503_maxcopyreadlen : Integer;
    sv503_maxcopywritelen : Integer;
    sv503_minkeepsearch : Integer;
    sv503_maxkeepsearch : Integer;
    sv503_minkeepcomplsearch : Integer;
    sv503_maxkeepcomplsearch : Integer;
    sv503_threadcountadd : Integer;
    sv503_numblockthreads : Integer;
    sv503_scavtimeout : Integer;
    sv503_minrcvqueue : Integer;
    sv503_minfreeworkitems : Integer;
    sv503_xactmemsize : Integer;
    sv503_threadpriority : Integer;
    sv503_maxmpxct : Integer;
    sv503_oplockbreakwait : Integer;
    sv503_oplockbreakresponsewait : Integer;
    sv503_enableoplocks : BOOL;
    sv503_enableoplockforceclose : BOOL;
    sv503_enablefcbopens : BOOL;
    sv503_enableraw : BOOL;
    sv503_enablesharednetdrives : BOOL;
    sv503_minfreeconnections : Integer;
    sv503_maxfreeconnections : Integer;
  end;
  PSERVER_INFO_503 = ^SERVER_INFO_503;


function Get_Computer_Name: string;
var
  dwlen: DWORD;
begin
  dwlen := MAX_COMPUTERNAME_LENGTH + 1;
  Setlength(Result, dwlen);
  GetComputerName(pchar(Result), dwlen);
  Result := StrPas(pchar(Result));
end;

function GetDomainName : string;
var
  err : Integer;
  buf : pointer;
  fDomainName: string;
  wServerName : WideString;
begin
  wServerName := Get_Computer_Name;
  err := NetServerGetInfo (PWideChar (wServerName), 503, buf);
  if err = 0 then
  try
    fDomainName := PSERVER_INFO_503 (buf)^.sv503_domain;
  finally
    NetAPIBufferFree (buf)
  end;
  result := fDomainName;
end;

Beispiel :

procedure TForm1.Button1Click(Sender: TObject);
begin
  Label1.Caption := GetDomainName;
end;