Determine the domain in which a computer belongs?

Use the Win32_ComputerSystem class and check the value of the Domain property. You can also use the DNSDomain property in Win32_NetworkAdapterConfiguration.

const
  wbemFlagForwardOnly = $00000020;
var
  FSWbemLocator : OLEVariant;
  FWMIService   : OLEVariant;
  FWbemObjectSet: OLEVariant;
  FWbemObject   : OLEVariant;
  oEnum         : IEnumvariant;
  iValue        : LongWord;
begin;
  FSWbemLocator := CreateOleObject('WbemScripting.SWbemLocator');
  FWMIService   := FSWbemLocator.ConnectServer('localhost', 'root\CIMV2', '', '');
  FWbemObjectSet:= FWMIService.ExecQuery('SELECT Name,Domain FROM Win32_ComputerSystem','WQL',wbemFlagForwardOnly);
  oEnum         := IUnknown(FWbemObjectSet._NewEnum) as IEnumVariant;
  if oEnum.Next(1, FWbemObject, iValue) = 0 then
  begin
    Writeln(Format('Computer Name %s Domain %s',[FWbemObject.Name,FWbemObject.Domain]));
    FWbemObject:=Unassigned;
  end;
end;

Determine whether a computer is a server or a workstation?

Use the Win32_ComputerSystem class and the DomainRole property.

Value	Meaning
0 (0x0)	Standalone Workstation
1 (0x1)	Member Workstation
2 (0x2)	Standalone Server
3 (0x3)	Member Server
4 (0x4)	Backup Domain Controller
5 (0x5)	Primary Domain Controller

const
  wbemFlagForwardOnly = $00000020;
var
  FSWbemLocator : OLEVariant;
  FWMIService   : OLEVariant;
  FWbemObjectSet: OLEVariant;
  FWbemObject   : OLEVariant;
  oEnum         : IEnumvariant;
  iValue        : LongWord;
begin;
  FSWbemLocator := CreateOleObject('WbemScripting.SWbemLocator');
  FWMIService   := FSWbemLocator.ConnectServer('localhost', 'root\CIMV2', '', '');
  FWbemObjectSet:= FWMIService.ExecQuery('SELECT DomainRole FROM Win32_ComputerSystem','WQL',wbemFlagForwardOnly);
  oEnum         := IUnknown(FWbemObjectSet._NewEnum) as IEnumVariant;
  if oEnum.Next(1, FWbemObject, iValue) = 0 then
  begin
    case FWbemObject.DomainRole  of
     0: Writeln('Standalone Workstation');
     1: Writeln('Member Workstation');
     2: Writeln('Standalone Server');
     3: Writeln('Member Server');
     4: Writeln('Backup Domain Controller');
     5: Writeln('Primary Domain Controller');
    end;
    FWbemObject:=Unassigned;
  end;
end;

Determine the computer name?

Use the Win32_ComputerSystem class and the Name property. You can also use the DNSHostName property in Win32_NetworkAdapterConfiguration.

const
  wbemFlagForwardOnly = $00000020;
var
  FSWbemLocator : OLEVariant;
  FWMIService   : OLEVariant;
  FWbemObjectSet: OLEVariant;
  FWbemObject   : OLEVariant;
  oEnum         : IEnumvariant;
  iValue        : LongWord;
begin;
  FSWbemLocator := CreateOleObject('WbemScripting.SWbemLocator');
  FWMIService   := FSWbemLocator.ConnectServer('localhost', 'root\CIMV2', '', '');
  FWbemObjectSet:= FWMIService.ExecQuery('SELECT Name FROM Win32_ComputerSystem','WQL',wbemFlagForwardOnly);
  oEnum         := IUnknown(FWbemObjectSet._NewEnum) as IEnumVariant;
  if oEnum.Next(1, FWbemObject, iValue) = 0 then
  begin
    Writeln(Format('Computer Name %s',[FWbemObject.Name]));
    FWbemObject:=Unassigned;
  end;
end;

Find the name of the person currently logged on to a computer?

Use the Win32_ComputerSystem class and the UserName property.

const
  wbemFlagForwardOnly = $00000020;
var
  FSWbemLocator : OLEVariant;
  FWMIService   : OLEVariant;
  FWbemObjectSet: OLEVariant;
  FWbemObject   : OLEVariant;
  oEnum         : IEnumvariant;
  iValue        : LongWord;
begin;
  FSWbemLocator := CreateOleObject('WbemScripting.SWbemLocator');
  FWMIService   := FSWbemLocator.ConnectServer('localhost', 'root\CIMV2', '', '');
  FWbemObjectSet:= FWMIService.ExecQuery('SELECT UserName FROM Win32_ComputerSystem','WQL',wbemFlagForwardOnly);
  oEnum         := IUnknown(FWbemObjectSet._NewEnum) as IEnumVariant;
  if oEnum.Next(1, FWbemObject, iValue) = 0 then
  begin
    Writeln(Format('Current logged user %s',[FWbemObject.UserName]));
    FWbemObject:=Unassigned;
  end;
end;

Rename a computer

Use the Win32_ComputerSystem class, and the Rename method.

const
  wbemFlagForwardOnly = $00000020;
var
  FSWbemLocator : OLEVariant;
  FWMIService   : OLEVariant;
  FWbemObjectSet: OLEVariant;
  FWbemObject   : OLEVariant;
  oEnum         : IEnumvariant;
  iValue        : LongWord;
begin;
  FSWbemLocator := CreateOleObject('WbemScripting.SWbemLocator');
  FWMIService   := FSWbemLocator.ConnectServer('localhost', 'root\CIMV2', '', '');
  FWbemObjectSet:= FWMIService.ExecQuery('SELECT * FROM Win32_ComputerSystem','WQL',wbemFlagForwardOnly);
  oEnum         := IUnknown(FWbemObjectSet._NewEnum) as IEnumVariant;
  if oEnum.Next(1, FWbemObject, iValue) = 0 then
  begin
    FWbemObject.Rename('NewName');
    FWbemObject:=Unassigned;
  end;
end;

Retrieve only local groups using WMI

Use the Win32_Group class and include the following WHERE clause in your WQL query.

Where LocalAccount = True

const
  wbemFlagForwardOnly = $00000020;
var
  FSWbemLocator : OLEVariant;
  FWMIService   : OLEVariant;
  FWbemObjectSet: OLEVariant;
  FWbemObject   : OLEVariant;
  oEnum         : IEnumvariant;
  iValue        : LongWord;
begin;
  FSWbemLocator := CreateOleObject('WbemScripting.SWbemLocator');
  FWMIService   := FSWbemLocator.ConnectServer('localhost', 'root\CIMV2', '', '');
  FWbemObjectSet:= FWMIService.ExecQuery('SELECT * FROM Win32_Group Where LocalAccount = True','WQL',wbemFlagForwardOnly);
  oEnum         := IUnknown(FWbemObjectSet._NewEnum) as IEnumVariant;
  while oEnum.Next(1, FWbemObject, iValue) = 0 do
  begin
    Writeln(Format('Local Account %s - Name %s - SID %s - SID Type %s - Status %s', 
    [FWbemObject.LocalAccount, FWbemObject.Name, FWbemObject.SID, FWbemObject.SIDType, FWbemObject.Status ]));
    FWbemObject:=Unassigned;
  end;
end;

This post is based in the MSDN entry WMI Tasks: Accounts and Domains