Remove the window from the inside of the house. Push a horizontal sliding window up, and then and pull it out from the bottom.
Examine the wheels on the bottom of the window for breakage or deterioration.
Remove any damaged wheels by prying them out with the flat head of a screwdriver. If the wheels are secured with screws, remove the screws first.
Buy matching replacement wheels from a home supply center or hardware store.
Snap or screw in the replacement wheels, and replace the window.
Clean the window tracks with a mild cleaning product and a soft cloth. Clean both the top and bottom tracks thoroughly.
Dry the tracks using a soft cloth.
Spray the entire length of the tracks using a silicone spray lubricant.