If you have backed important files/folders/licenses under the old user, then you can delete it now.
be sure that the preferred account you are using now is an administrator account and not the restricted/ordinary user account.
under windows vista/7/8.x, only administrator accounts can install/uninstall/modify any file.
an ordinary account can only install/uninstall some programs and may require administrator privilege even as simple as updating adobe flash (under windows xp, at least).
some program licenses are hidden under the user account that installed it.
( I can't remember a giveawayoftheday startup tweak program I used many years ago in which the license code is hidden under windows 8 folder C:\Users\usernamehere\AppData and similar location under windows 7/vista)
edit: the program I previously forgot is
wirekeys. the program author's website is no longer accessible.