As I was cleaning the windows before winter, I noticed that a lot of the caulking outside has cracked and come away from the window sill. I also noticed that if I push down on the bottom of the frame, it moves up/down about 1/16 of an inch. Then I saw that there are two screw holes in the frame which the previous owner must've put in there. The windows aren't too old, they're typical cheapo department store windows.
The question: is it OK to drive screws into the bottom of the window frame to secure it in place? Will it warp in the summer? This isn't the only window to have such holes in the frame, and we haven't noticed any water damage in the past couple of years.