I don't have "PhotoMechanicInstaller.msi"
I have update installer packages, thus:
PMPlusSetupR6097.msi (new, will not install as explained above)
PMPlusSetupR6026.msi (previous -- I have this version installed and running without problems. I don't do anything fancy, so I really can't tell if there's problem with this build, Ver 6.0, build 6026)
fyi.. Windows Pro 10, 64 G memory, terabytes of open storage, my computer is not the problem