If you're running Active Directory, the easiest way is to use Group Policy to create a software installation. See the link below. I performed an upgrade to Viewmail using a GPO a while back and it went great. One thing to be aware of is the upgrade will reset the playback and recording devices to the default of phone.
How to use Group Policy to remotely install software in Windows Server 2003
My GPO is applied at the domain level and is Assigned as opposed to Published so that all users get the software. The package is on a network share accessible by all users. The GPO is not set to upgrade any previous package. The VMO installation takes care of looking for and removing any previous version.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.