Take the glass out of the window. If the window is single-paned, unscrew the bolts that hold it in the frame. Lift the window out of the frame if it's a sliding window.
Remove the fixed window from the frame if the window is a sliding window. Soften the adhesive that holds the window in place by heating the frame with a blowtorch.
Cut into the window frame at the corners and the joints, using a reciprocating saw that has a metal-cutting blade.
Remove the frame from the brick wall by prying it out with a hammer and pry bar. Place a wooden block between the brick wall and the pry bar to protect the brick wall from damage.