Since you said Program files the size of each installed program is listed in "Add and Remove Programs." Do not go making manual changes in "Program Files." Those are your installed programs and you could end up making a lot of trouble for yourself. As far as other files are concerned, "Folder Options" will allow you to set the display, and under "View" at the top of each window you can select "Details" which will give you the size of each file. If not, under "View>Choose details," just check the box for size.