[2016.07.20 Edit] Install XE10.1 Berlin at D:.
C: > 26.9 GB
D: > 30 GB
Install main program at D:, and others at C:, download file at removable disk.
C: > 27 GB
D: > 30 GB
T: > 30 GB
Boost for XE10 requires additional disk space
[Reference] http://docwiki.embarcadero.com/RADStudio/Seattle/en/Installation_Notes