"The Windows" in this metaphor refers to the speaker's eyes or ability to see. When the speaker gets closer to passing away, the "Windows failed," signifying his losing vision as his life approaches to an end. By associating the closure of windows with the actual act of dying, such as losing consciousness and sight, this metaphor suggests a barrier separating the individual from the outside world as they approach death. The use of the phrase "I could not see to see" highlights the speaker's complete loss of vision and reinforces their incapacity to notice anything beyond this last instant.