Excel Add-ins after a server change

We have a number of copies of Excel that where installed via network install
from an old server. Now, when I try to install an Add-in, the install stops
when it tries to install some component from the old network install
location. So far as I can tell, I can't change the path (at least in the
dialog), nor is there a browse button. Is there somewhere in the registry
where I can change the install search path, or do I need to uninstall, then
reinstall from the new network install path, then install the add-ins?

Best,
Gordon