Moving postgresql data to different drive
The following should do it:


Shut down PostgreSQL
Make sure PostgreSQL does not run any longer
Check that PostgreSQL is really stopped
Copy the old data directory to the new drive This is usually defined through a commandline parameter  (-D) for your service or through the PGDATA environment variable.
Update your PostgreSQL configuration (service, environment var) to point to the new data directory.
If you copied the data, rename the old data directory to make sure PostgreSQL cannot find it any longer. That way you'll get an error message if you didn't get the configuration right. 
Start the service
If everything is running fine, you can delete the old directory.