@
alternety - I get the feeling that you might be over-thinking things.
If there's no metadata.db file in the said folder, then by definition its not a calibre library, its the presence of the metadata.db file that 'defines' the folder as a valid calibre library.
If the library
with it's metadata.db file is still on the boot drive then use calibre's
Library->Switch/Create->Move current library to new location feature - eg the following would move the library at
D:\Calibre Libraries\_Main to
G:\Somewhere
Calibre plugins are zip files, you don't have to do anything other than install them. Most PI's are here ar MobileRead ==>>
Calibre Plugins @ Mobileread. There's a sticky thread with an index at the top of that sub-forum. You can get the PI's you see there there via
Preferences->Plugins->Get New plugins.
The DeDRM PI is an exception, it must be installed installed manually via
Preferences->Plugins->Load plugin from file, just browse to the zip file you downloaded and press OK.
BR