just dont use WD40.... good on hinges.. not so good on door tracks.... it got my tracks all sorts of gummed up... ldub mentioned some stuff called Jig-a-loo that comes in an orange can.. i found mine at home depot.. my windows seemed to slow down when i first used it and i cursed his name... then after a couple of hours my windows worked beautifully.. so i retracted my cursing of his name heh (sorry u had to find out this way dub)

also when u do that esp the first time.. take a popsicle stick the back end of a spoon or something like that wrapped in a paper towel or shop rag (wrap it a couple times to make sure you dont tear through and scrape the track) and run it up and down inside the window channels to clean some of the gunk in there... that gunk will slow your windows down too