My local Wal-Mart didn't have the CRC or Valvoline brands of silicone spray recommended in the last thread like this, so I tried the Gunk/Liquid Wrench Heavy Duty Silicone Spray they had. My windows had gotten some dust in the tracks recently, and were starting to sound "gritty" when I'd move them up or down. While they didn't sound good going up and down before using the spray, at least they moved free and straight with no help from me.

Now I don't know if my window tracks had dried out over time or what, but it seemed like the silicone spray must have caused them to swell up a bit because the spray actually made my windows start binding. After not using them for a few days, the binding problem cleared up some, but after that episode, I think I might try the graphite powder next time.