Hm.
Well that just means that
1, FeralHeart is running, so close it.
or 2, Your computer is trying to run the uninstaller.
(Or possibly 3, which is I don't know. :3)
If FeralHeart isn't running, shut down your computer, turn it on again, and then go delete the FeralHeart folder.
As for the admin thing, usually you can just click something that will allow it to delete, as long as you are the admin account on your computer, meaning there are no other log ons?