I have a 1940 house and the basement windows have a steel frame that is mortared in. I recently removed one and it was a piece of cake. I just revoved the tilt-in sash and then I was able to take a pry bar and pry the top and bottom in towards the center. After doing this I just worked the sides in and with a little tug, I was able to pull the steel frame out. I'm planning on replacing the 8 remaining windows. I have a brick exterior so I have a 1" cavity between the brick and the concrete, so I am planning on replacing the windows with a standard size basement window and building the frame to fit the window.