I'm the Administrator of Computer, but can't rename or delete folders??

Restarting Computer had no effect. :(

Edited to add:
I even tried a System Restore, that didn't even complete! (The restore failed twice!) What on Earth is going on here??? This computer has had no problems until now! Has this stupid Sims 3 folder totally messed up my computer??

How do I give myself permission to delete this folder?? It says to get permission, but gives me no clear way to do so! I can't rename the folder either, it claims it's being used by another program. Why can't it tell me what program is using it?