Traditional double-hung windows operate by way of a sash and balance system. This is sometimes called a sash and ballast system, because the sash is counterbalanced by a weight. If you live in an older home with original windows, chances are they feature a sash and balance system. Sometimes the cord on the sash and balance system wears and breaks. This will make the window difficult to open and close and perhaps inoperable. You can repair the ballast or balance system as a do-it-yourself project.
Look on the sides of the window frame for a rectangular panel. Some windows have this panel and some do not. This is called a knockout panel or a pocket cover. It provides easy access to the sash cord and balance. Unscrew the screws on the panel with a screwdriver. Lift the panel off the side of the window frame.
Remove the trim molding if the window doesn't have a panel. Score along the edge of the molding with a utility knife to break the paint seal. Unscrew the screws in the trim molding with a screwdriver and pull off the molding.
Inspect the now-exposed sash cord on each side of the window frame. Pull the balance weights out. Untie or cut the cord from the balance and the hook on the window sash with a utility knife. Ask an assistant to hold the window sash in place or prop it up with a scrap board while you replace the sash cord.
Tie one end of the replacement sash cord to the balance. Thread the opposite end of the sash cord through the pulley and tie it to the hook on the side of the sash. Once the sash cord has been replaced, release the window by either having the helper let go or removing the scrap board. Replace the panels or trim molding.