Remove the inside sash using a small pry bar. Cut any sash ropes with a utility knife to let the weights fall into the wall to remove the sash from the window jamb. Remove the parting bead, which is the small piece of wood between the inside and outside sashes. Finally, remove the outside sash.
Open the access door on the jamb with a screwdriver. This door is located about 12 inches up on the jamb. This door allows access to the weights without having to remove interior trim. If the windows are very old, you may have to remove the interior trim to access the weight.
Replace the ropes using nylon cording. Make sure the pulleys are able to move freely. Scrap any excess paint away with a screwdriver. Tie the end of the nylon cord to the weight. Return the weight back through the door.
Complete sash repairs. Remove excess paint from the sashes. If they need to be repainted, do so at this time. Do not paint the edges of the sashes. You can apply wax to the sash edges to help the windows slide.
Knot the rope so it matches with the knot holes on the sash. Make sure that these new rope and knots will allow the window to open fully.
Hold the outside sash up against the jamb. Place your knots into the knot holes. Use a small nail to hold the knot in place. Tilt the outer sash into the jamb and replace the parting bead. Replace the inner sash the same way.
Repair any trim damage with sandpaper, caulk and paint.