Remove the casings, stool, apron and take the frames out of the opening.

Once you have removed all the casings your window will look like this...

The flat ledge board at the bottom is the stool, and the trim board below it is the apron board.  These are often nailed in pretty well, so get out the crowbar, saw or whatever it takes to rip them out.

Here's the end of the interior demolition:

Now you can remove the window sashes (the actual framed glass pieces), remove the storm windows, cut the sash cords for the counterweights, and remove the window frames.  The window frame is nailed into the rough opening and you will have to pry it, cut it with a circle saw or Sawzall, bang it out with a hammer, etc. I like to use a hard rubber mallet.  The wood will splinter, so wear those glasses.  Keep in mind you will not be reusing any of this material here, so go nuts.  You should be able to recycle the iron weights and do what you can to reduce landfill by re-using the lumber if you have do other projects.