Window replacement can be a do-it-yourself project. To replace a window, measure the dimensions of the old window, pry off the stops, remove sash, remove the old window, and mount a new window. Required tools include a utility knife, square, small pry bar and tape measure.
Correctly measure the height and width of the window. Remove the stop pieces, and retain them for reuse. Pry off the inside sash. Push the outside sash to the bottom, remove the parting beads, and pry off the outside sash, taking care not to pull it with the outside stops.
Clean the sills and jambs, and seal any holes with wood putty. Apply caulk on the inside of the exterior stops, designate the sill angle, lay a bead of caulk on the sill angle, and install it. Place a header on top of the window, and caulk along its top.
Purchase a window of the same size as the old one. Squarely position the window in place, and secure it to the side jambs with mounting screws. Push the header to fill any gap between the frame and the window, and then screw it in place. Caulk and replace the inside stops.