Take your utility knife and slide the blade along the seam between the timber moulding of the architrave and the wall. Gently cut through any layers of paint that may be covering the seam and create a clean gap between the moulding and the wall. This will help stop the paint peeling off the wall when you pull the architrave away from it.
Now use your hammer and chisel to start pulling the architrave away from the wall. Wedge the chisel in the gap and gradually work your way around the timber moulding, using gentle hammer taps to avoid splitting the timber or the damaging the wall. Carefully pull the timber moulding away from the wall to loosen any nails and to make the gap wider.
Now take your pry bar and wedge it in behind the timber. It's a good idea to also wedge a packer between the pry bar and wall so that you don't mark or dent the wall. Then use the pry bar to pull the timber away from the wall. There will be a lot of exposed nails in the timber so wear gloves when handling it for added protection.