Windows XP and Vista remembered individual Explorer folder sizes and positions.
Starting with Windows 7, Explorer windows do not remember individual folder window sizes and positions. Each folder window shares the same size, and their position cascades (the next one appears slightly below and to the right of the previous one) as more windows are opened.
If you maximize one window and close it or resize it to a big enough size such that it has no room to cascade, all Explorer windows will open maximized or at that specific size.
There was a program for Windows 7 called ShellFolderFix:
http://www.sevenforums.com/free-develop ... -size.html that tried to save Explorer window positions and size. I haven't tried it on Windows 8. Maybe it will work for you.