Password Caching IE5/Proxy Server 2.0

How do I disable password caching in Internet Explorer 5.0? I currently have IE5 pointing to our Proxy Server, which is set for authentication. I’d like it if users didn’t have the option to save their password to their password list. Any ideas on how to make this option go away? I have IEAK and have searched through each option, looking for something that says “disable password caching” but so far I’ve been unsuccessful.