How to recover Data

I had a m/c with Postgres 7.2 and huge amount of data. on Power
failure and restart of the m/c pgsql refused connect to any of the
database. Being an invoice i took a tar of the data dir.
I tried reinstalling PGSQL and copied the data dir to the same dir
where the new data is being stored. ie
cp /backup/pgsql/data /var/lib/pgsql/data

When i connect to the old database i am able to connect but when i do
a \d to list the tables i get no relations found. Also when i do
select * from a table i am able to get the structure but it has no
records in it.
WHen i check the same info in pg_database to check if the old database
entry is present i dont find it.
Can someone help me as to how to recover my data???
Basically what i feel is update the pg_tables.
Thanks and rgds
Padmanab