Short version: W10 PC, I can't upgrade or even uninstall my current version of Express without the *old* .msi file, which is missing. It seems it needs access to the old .msi to remove the old version of the software, and then the new .msi to install the new version. I can download the new .msi files fine but they won't run for this reason and I can't just remove the software manually without help. There used to be a Microsoft FixIt which helped with this kind of thing but that is no longer available either. Old Express won't fire up as it's a pre-GDPR version.
So I think I need either access to the old .msi, or a list of registry keys to squish (I am entirely comfortable using regedt32/similar to do this) to fool my computer into thinking I never had Garmin Express installed, so I can then install the new version "as new". However it may be that I need something else entirely :)
Very grateful for any help anyone can offer.