abort task on WinNT

[Alfred Hilscher <Alfred.Hilscher@icn.siemens.de>]

Hello,

I have a program consisting of a main procedure, handling user-input and
a local, free-running task. It looks like follows (schematic):

procedure p is
  task t is
  end t;

  task body t is
  begin
    loop
      null;
    end loop;
  end t;
begin
  null;
end p;

The problem I have is, the program must terminate immediately when the
user request termination. But due to the task running in a loop, it
doesn't (it waits for the task termination I think). I tried to insert
an "abort t;" at the end of "p", but it still doesn't terminate. In the
final solution, task t shall do remote communication (via serial or
TCP/IP). So maybe it waits for data transmission and will not be ready
for a rendevzous saying "shutdown". 
So my question is: how can I force immediate programm termination ?

I work on Windows NT 4.0