How do you fix a squeaky floor when carpeted

Answer 1 If you can pull up the carpet to get to that area, then you can screw or nail through the offending/sqeaking floor board into the subfloor and then put back the carpet. If you have a basement try to find where it sqeaks from below [while you are in the basement, have someone step on and off the offending spot]. Once you know which board(s) is loose, screw a screw into it from the floor joist, through the subfloor, into the offending floorboard. Hopefully, this will pull the squeaking floor board down against the subfloor, and make a tighter fit and stop the squeek. Or, from the basement, screw a piece of 2x4 onto the floor joist, and then screw through the 2x4 and subfloor,into the loose floor board, from below. Or, gently drive a shim between the sub floor and the floor joist to see if that works. That all the thoughts I have for you. Hope they work.