There isn't a straightforward method for this but you do have two options:
1. Install a different version of PostgreSQL (using another port) to your other drive.
2. Creating a database on another drive using the existing version of PostgreSQL needs to be done via PGAdmin (click your Windows Start button then type pgadmin and you should see it). Right click on your server in PGAdmin (where it says PostgreSQL x.y) and choose "New Object -> New Tablespace". Give it a name, set the owner to the postgres user via the drop down and enter your directory on the Definition tab. Once you have the tablespace, right click on where it says Databases and choose "New Database", give it a name and set the owner to the postgres user again. On the Definition tab, pick an existing PokerTracker 4 database as a Template and pick the tablespace you created (I recommend using an empty database as the template unless you want the data in that database copied over). You can then add that database to PokerTracker 4 via "Database -> Database Management -> New -> Browse Databases". If you've not used PGAdmin before you should
backup your poker data before making any changes there as making database changes outside of PokerTracker 4 is somewhat beyond the normal scope of our support and can break things if it's not done correctly.