Measure the interior width and height; the old frame dimensions match the standard vinyl window size. Order windows with insulated glass. Make an election regarding the style of the glass panes, as the new window may have a single pane or multiple panes.
It is important to check the condition of your existing window frames before installing vinyl. If rotten or badly out of square, the entire unit and frame may need replacing. The required tools for replacing or installing a vinyl window include a hammer, drill, tape measure, caulk gun, level and safety glasses.
Install the vinyl window from the inside. Remove and preserve the inside stop; this can be reused. Remove the lower window sash. Remove and discard the parting stop, remove the sash cord pulleys, and fill the weight pockets with insulation. The new vinyl windows should now be able to be pushed into place and held by mounting screws. Caulk around the outside edge, and install the trim pieces.