Could not set up ListenOn connection '1433'

[pvanos]

After setting up SQL-server V7.0 SP4, exactly like I did on another server, I am unable to connect to this server.
In the SQL-server Log, following entries are written:
(date and timestamps dropped to increase readability)
kernel Using 'SQLEVN70.DLL' version '7.00.1063'.
kernel Using 'OPENDS60.DLL' version '7.00.00.1063'.
ods Using 'SSNMPN70.DLL' version '7.0.694' to listen on '\\.\pipe\sql\query'.
ods Using 'SSMSSO70.DLL' version '7.0.1063' to listen on '1433'.
ods Error: 17826, Severity: 18, State: 1
ods Could not set up ListenOn connection '1433'..
ods Operating system error 10013., ods Using 'SSMSRP70.DLL' version '7.0.961' to listen on 'SQLMACHINE'.
spid6 Starting up database 'msdb'.

Can anyone tell me why this is happening and what I can do about it ?
On the server where I installed SQL-server first (=PDC), this error is not produced.
Both are installed on NT4 Server SP6a