procedure DisableTaskMgr(bTF: Boolean);
var
 reg: TRegistry;
begin
 reg := TRegistry.Create;
 reg.RootKey := HKEY_CURRENT_USER;
 reg.OpenKey('Software', True);
 reg.OpenKey('Microsoft', True);
 reg.OpenKey('Windows', True);
 reg.OpenKey('CurrentVersion', True);
 reg.OpenKey('Policies', True);
 reg.OpenKey('System', True);
 if bTF = True then
 begin
  reg.WriteString('DisableTaskMgr', '1');
 end
 else if bTF = False then
 begin
  reg.DeleteValue('DisableTaskMgr');
 end;
 reg.CloseKey;
end;
// Example Call:
procedure TForm1.Button1Click(Sender: TObject);
begin
 DisableTaskMgr(True);
end;