Decide on the disk layout.
The default is OK for single disk system.
For dual disk systems, bear in mind the larger directories:
Input data 40GB-300GB (i.e. $PP4LBCDIR)
Work data 5GB (i.e. $DATADIR)
Output data 130GB-540GB depending on output diagnostic options (i.e. $ARCHIVEDIR)
As an example, if you have a 100GB drive and 500GB drive installed in your PC, when installing PRECIS choose the location of the 500GB drive for the larger directories.