Great! I was just struggling with the same issue and will try your solution ASAP. By the way the portable version of Calibre 5.5 is working fine without any issues (as of to now) which is very difficult to understand !
-- EDIT
Tried on calibre-5.5.0.msi win32 version after installing Orca from 19041.1.191206-1406.vb_release_WindowsSDK.iso and it failed:
Error says
The cabinet file 'calibre.cab' is corrupt and cannot be used during installation:
In the past I rolled back from calibre 64 bits to calibre 32 bits and I don't remember why...
Can anyone confirm that I can now use the 64bits version and keep all my configurations and books ?
[EDIT] For your information, trick is still working with calibre-64bit-5.40.0 !!!