I tried an experiment.
I created a fairly long directory
Code:
C:\Users\peter\Documents\12345678\23456789\34567890\4567890\567890\67890\7890\890\90\0
and tried to install calibre portable in it. As expected, the error message that the path was too long was presented.
I did a
Code:
subst y: C:\Users\peter\Documents\12345678\23456789\34567890\4567890\567890\67890\7890\890\90\0
followed by
Code:
c:\Users\peter\Downloads\calibre-portable-installer-4.21.0.exe y:.\calibre_portable
and had no issues at all installing it, or subsequently running calibre_portable from the y: drive/