You best bet is to install a clean system on that box, install Unity 4.0 there and use DiRT to transfer your Unity data over - you can get the latest DiRT backup and restore versions off www.CiscoUnityTools.com.
You can certainly use other methods such as drive imaging software and the like but those have not been tested by the BU and aren't supported by TAC.
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.