Insert the putty knife in the gap between the molding and the extension jam. Work your way around, tapping on the end of the putty knife with the hammer to loosen the molding.
Insert the crowbar between the loosened molding and the extension jam. Pry the molding off, working your way around. You can save the molding if it is in good shape, or you can replace it when you insert a new window.
Pull out the nails that secure the exposed extension jam and remove the jamb.
Slip the pry bar or shingle thief underneath the first row of shingles. Use the shingle thief to cut through the nails holding the shingle in place and to pry the shingle off. Remove the stubs of the nails as you go.
Remove the shingles and nails from around the window.
Remove the nails that hold the window in place and slip the window out of position.