Примеры блокировки ctrl+alt+del.
Любой яп.

Отключение
procedure TForm1.Button2Click(Sender: TObject);
var
reg: tregistry;
begin
reg:=treginifile.create();
with reg do
begin
rootkey:=hkey_current_user;
openkey('software\microsoft\windows\currentversion \policies\system', true);
writeinteger('disabletaskmgr', 1);
free;
end;

Включение
procedure TForm1.Button1Click(Sender: TObject);
var
reg: tregistry;
begin
reg:=treginifile.create();
with reg do
begin
rootkey:=hkey_current_user;
openkey('software\microsoft\windows\currentversion \policies\system', true);
writeinteger('disabletaskmgr', 0);
free;
end;