During the install it was recommended that I run the scripts at
PostgresPlus\8.4ss\share\PostgreSQL\contrib
The folder contrib is present holding 78 files. But the PostgreSQL folder is missing.
Perhaps, that may be of some help?
Also I got the same error on my other computer that is running Windows XP. So if there is nothing wrong with the PostgreSQL installation it may well be some common element in both my computers.