I need to access my messages, but the Administrator is no longer available, and I have no idea what the user passcode is.

Ok there are two things you can try here the first this is you can right click on the application and run as administrator should be an option that should get you around that problem. Now to run the updater in safe mode to try and fix your problem should also be an easy fix. When you start up your computer and you get to the section ware it asks you how you would like to boot one option should be to boot in safe more with networking this will allow you to access your systems in safe mode and the internet by loading all needed drivers and processes for networking allowing you to access the internet.

I hope this helps.

Thank you,