tcp port

Hi,
port 5432 (postmaster postgres reserved) on my machine(suze 8.2), with
PostgreSQL 7.4.1 ) is unreachable
When i launche postmaster with tcp/op option, i've the message :
LOG:  could not bind IPv4 socket: Address already in use.
HINT:  Is another postmaster already running on port 5432? If not, wait a few
seconds and retry.

I've launched nmap (nmap localhost -p 5432), port scanner and got :
The 1 scanned port on localhost (127.0.0.1) is: closed.

I suppose having mis-uninstalled an old version of postgres

Any idea ?

thanks
philipe