[bookishh]

Well, to make it more concise.

On my Windows 7 (64bit) , when I today installed newest Calibre (3.37.0 64bit), it wanted to deinstall previous Calibre version I had on the computer.

However, at the point of deinstallation of old version , it DID ask me for location of calibre-64bit-3.11.1.msi -- 3.11.1 being the previous version of Calibre I had.

The idea is that Windows usually silently keeps a copy of MSI files it ran, in C:\Windows\Installer\ directory (under GUID filename, rather than the original filename you downloaded, no less), AND if that file is kept, it finds it automagically at the point of uninstall. That's why, if you don't delete MSI from that directory, it doesn't need one from your original Download directory.

However, I do clean up C:\Windows\Installer directory occasionally (it is once again rife with 7GB of MSI files anyway, since I haven't deleted a number of more recent installs), therefore W7 couldn't find the MSI, so it asked me for it -- remembering to use the Download directory and original filename I had, too.

Since I didn't have it, new Calibre installation couldn't delete old version, and after finishing, I had 2 versions of Calibre on the computer.

If you want to duplicate the behaviour, delete everything from C:\Windows\Installer\ and try to uninstall Calibre.

I am sorry I am not very good with MSI, but as per the link quoted in the OP, the deinstall should run well even if the MSI of the original installation is not available, so I think this is a sort of a bug.