Try WD-40. Seems like you can't go wrong.
WD works as Steve said, So does silicon spray. Personally I prefer the silicon spray as its not oily which attracts more dust that also binds the tracks.
It is very common for sliders to begin to stick after a few years time. There are rollers on many sliding windows as well. All depends upon the manufacturer of the window itself. After time the adjustments of these wheels that support the window section alone can get out of whack causing the window to bind much like what is happening to you now. On the vertical ends of the slider you may see some screws near the bottom, or you may even see a plastic button type cap on the face about one or two inches in from the corner near the bottom. Turning this screw, or removing the cap and turning the screw that is hidden behind should change the way really sits on the track. Oftentimes resulting in a window that works much better.
Bernice, if your really not sure of what to do, take some photos of the windows in question, both distance shots, and photos of the edges, and corners of the windows themselves. Post them here if you did not figure out how to adjust the window and I will see what I can suggest on how to move ahead.
Thank you Bob and Steve, yer gud peoples!
Windows are working great! Just thought I would let you both know.
We did honey do's this last weekend, including hosing down the "house" , washing windows and screens (and sending the little spiders inside, but that was just an added bonus)! Anyway I sprayed the tracks with silicone spray and they work super fine now.
Thanks so much! And I will keep an eye on the adjustment issue!
Great. Glad to hear it worked for you.
Me too, I love when things work the way they should , with a little tweaking! Sigh of relief! Thanks again!