That sounds strange to me and I think you don't have a clean installation of Mp3Tag.
Are you really using Mp3Tag under a user name "admin"?
Is it a portable installation?
M3Tag uses this temp folder for portable installations.
I'm just speculating as to the cause and am absolutely not sure if I'm right:
You start Mp3Tag under an account with administrative rights from another user account. Mp3Tag uses this temporary path to which your standard player has no access rights.
Maybe @Florian can correct me or confirm.