So, you are trying to wiretap Ewan's computer for the first time? Do you have the clips from Moira's safe box?
Also, try reading over the steps in the walkthrough:
Go to Cathedral control room.
Thermostat: Go to the server. Go to the back left aisle - B3. See the thermostat.
Raise or lower the temperature by using the arrows at right of the readout until an alarm is heard.
Hear Ewan get upset. Learn that Ewan has to reset the thermostat himself and be away from his desk.
Hiding place: Go back to the server room and look for a place to hide.
Enter the first aisle at left while facing the exit - B1. See the main computer server which is placed in a recess.
Divert Ewan: Time to get Ewan away from his desk.
Raise or lower the temperature until an alarm sounds.
Back up, back up, turn left, forward, left to enter the first aisle on the left and go curved right into the recess.
Find the computer main drive: Once Ewan enters and passes by - exit the server room and go to Ewan's desk.