We’re currently deploying Fix Pack 3 for Lotus Notes 8.5.3.

But before we do that, we need to do an uninstall of s Post Fix Pack 2 RSS hotfix.

The uninstall was failing with a MSI error 1603.  Aaron Stebner’s post on locating 1603 error causes was not helpful with this.  I tried installing Fix Pack 3 over the RSS Hotfix but it failed.

The uninstall command we were using looked something like this:
msiexec.exe /i ClientUpdate.msi

There are some products which state that their uninstall string is to use the msiexec.exe parameter “/i”.  “/i” for install.  This was one of those products.*

I changed the “/i” for an “/x” (uninstall).

Fixed! (kind of).  The uninstall was now reporting a MSI error 1605
This action is only valid for products that are currently installed.

But we make progress!  The “/x” uninstall, even though it returned a 1605 error, managed to remove the references to the RSS hotfix from the Registry.

Which then allowed Fix Pack 3 to install.  Success!

* –  I suspect that some products do this so they get the opportunity to display a “nag” screen aka “Do you really want to uninstall me?”