File systems backup problem

I'm new to postgresql . I use the version 7.2 on RedHat 7.2

I have made a mistake. I drop a database but not the good database.
And I have a file systems backup.
But what I didn't know until now, is that the postmaster should be stop in
order to make the backup.
So when the backup is made, the postmaster isn't stop.
And now when I want to use the backup in order to restore the database I
drop, this doesn't work.
The files are restored but when I restart the postmaster and want to
connect to the restored database,
the postmaster reply that it doesn't know the database in the system
catalog.

Is there a solution to repair the database ?

In advance, thanks for your reply.

Malaspina Loic
www.focalsystems.fr