I am upgrading a Unity system (unified communications with Exchange 2003) that was set up by someone else from 4.x to 5.0. I have the login account and password for the OS (windows administrator), and I also have the account for the Unity web administration. Other than that, I do not know any other accounts or passwords. There is someone else that administrates the Exchange side of the configuration. Do you know if I will encounter any problems with the upgrade, or a way for me to check the other possible accounts used for the Unity Installation?
You will need the unityinstall account for the upgrade.
All the users are in your AD, attached is information about the users you need to have in the system, which services use them and how to reset the passwords if needed.
The name of the users might not be the same in your system but most users follow the guide using those names to avoid confusion.
Creating Accounts for the Installation and Granting Permissions
Appendix: Cisco Unity 5.x Services
How to Change the NT Password for the Exchange and Unity Service Accounts