Examine the storm window to determine if the frames were painted together. Score the paint with a utility knife to separate the frames.
Lift the lower sash upward until you can see the bottom frame beneath it. If the storm window includes a clip system, the window will stay in place as you raise it.
Pull the bottom of the lower sash toward you, and then downward until it clears the inner frame. Lift the lower sash upward and pull the bottom out to clear the window ledge. Set the lower sash aside in a safe location.
Push the fixed sash upward with your fingernails until it separates from the lower screen. Pull out the bottom of the fixed sash toward you and pull downward to clear the frame. Slide out the upper sash and place it in a safe location.