Restoring Database from Data directory backup.

Using XP Pro and Postgres 8.3
I made a backup of the "Data" directory of the Postgres Installation
to another place on the hard disk.
Now the customer has uninstalled postgres then reinstalled a new one.
Of course the original tables are all gone.
Is there a method of retrieving the original tables and data from the
backedup Data directory.
I hope so or I am in shit.