If all you did was upgrade. You should see a folder in c:\ called "windows old"
It'll have all your old stuff in there so assuming defaults you should have C:\windows.old\program\files\ square enix.. etc and can find your Final Fantasy XIV directory. all you need to do is copy it somewhere else. like c:\program files.
This should also work for settings. In the windows.old folder find users\youraccount\documets\my games\Final Fantasy XIV. And copy that folder into your new users\documents\my games folder. And all your settings will be restored. (this one windows should do itself but just in case)