I cannot delete the Bonjour folder because I get a message that access is denied for both the mdnsNSP.dll file and the mDNSResponder.exe. How do I delete these files?

I'm trying to fix my installation of iTunes 11.1.4. Part of the instructions tells me to delete the Bonjour folder from my Program Files. However, when I try to delete the folder, or either of the remaining two files (mdsnNSP.dll or mDNSResponder.exe), I get the following message:

"Cannot delete <file name>: Access denied. Make sure the disk is not full or write-protected and theat the file is not currrently in use."

How can I delete these files so that I can re-install iTunes 11.1.4?