grouping

oracle 9

I have a table with task_id , order_id , and status in My problem is I only want to get orders out that have all "COMP" or ALL "COMC" or all are "COM*"
The sql works but is very very slow
Any ideas please

task id order id        status
1       a       COMP
2       a       COMP
3       b       COMP
4       c       COMP
5       c       COMC
6       c       COMC
7       d       COMP
8       d       COMP
9       d       ACT
10      d       EXC
11      d       ACT
12      e       COMP
13      e       COMC
14      e       ACT
15      f       COMP
16      f       COMC
17      g       ACT

Sql problem
select distinct t.order_id from tasks t,tasks t0

                 where t.order_id  = t0.order_id
                                 and t.STATUS = 'COMP'
                 and t.order_id not in (
                 select order_id from wm_tasks
                 where STATUS NOt in ('COMP' ,'COMC')
                 and order_id in (
                 select distinct t.order_id   from wm_tasks t,wm_tasks t0
                        where t.order_id  = t0.order_id
                        and t.STATUS = 'COMP'));