Calibre2 is not a normal (in any sense) name used for a Library
Calibre2 IS the name of the PROGRAM FOLDER (on Windows).
The
default (AKA hinted name) Library is Calibre Library with no requirement to
accept it 
.
Once Calibre has been installed, it remembers (the settings) of all recently used Library names, even if uninstalled, the settings remain.
What you describe implies the settings were corrupt, therfore not useable and a erroneous library location was then entered