Accessing permissions

Hello everybody

You know firefox browser stores my profile settings, plugins, bookmarks
....etc on
users --> *username* --> application data

now I cannot access these folders at all as an error message appears says
that I don't have permission to access these folder, and I must find a way to
access it to get a copy from this important folders and files.

I have only one user account on vista and it shows that it the
"administrator" on the computer, if so why I can't access any and all folders
on the drive C ?

one mre question, how can I move my account username to to put it under the
administrators group in windows vista? not to be just an administator user?

Thanks a lot