Upgraded to Win8, account problem

So I upgraded to Win8, and I have an account folder named my old Win7 username, however for Win8 I set a new username - yet the user folder is still named what it was in Win7.

Also when I try to delete windows.old it prompts me "You need permission from PCNAME/OldWin7Username"

How can I rename the folder?

Hi
Folders you do not need to rename it.
Right-click on the C drive. According to the following: