A dropping window is usually caused by the window shoes coming off the pivot bar:
A. Using a flat bladed screwdriver, insert it into the metal part of the shoe that has a "U" shape grove in it. The upright "U" is the locked position.
B. Using a decent amount of force, turn the screwdriver clockwise until the "U" turns into a "C" shape. This is the unlocked position.
NOTE: The shoe is spring loaded. Make sure to hold the shoe so that it doesn't go all of the way up.
C. Bring the shoe up 3"-4" and twist the screw driver back counterclockwise to bring the grove back to the "U" or locked position. Now remove the flathead screwdriver that was holding the shoe.
D. Now bring the sash down to the level of the shoe.
E. With the tilt latch, tilt the window open. Ensure that the sash is level to the floor.
F. Press on the window near the shoe to force it into the shoe.
G. Close the sash.
H. Pull the sash UPWARD to ensure the shoe has engaged. If the shoe has not engaged, you will need to repeat step 4 through 7. If the shoe is properly connected you will not see it any longer and the window will function properly.
NOTE: Do not remove sash unless absolutely necessary.