if you go down on the floor level of the theatre there shud be a door on the left you may have to go up to it see it a lil better and you turn right as you go and by the end of the corridor should be a backstage/makeup room wake strait through there and at the end of that room turn right again and walk a couple of meters and if you look to your right there will be the stage with that computer you was lookin for be carefull because terrorist start tryin to kill you just after you have messed with the computer and once you killed lots of them you should see sum ladders you can go up at the left on the stage climb up there may be sum terrorists tryin to shout you when you get to the top and just simply kill them and your right by the end of the mission (note: this is the xbox360 missions i dont know if the ps3 versoin is different.) good luck gettin that computer and completing that mission;)...