creating a catalog for docbook.dtd 4.2.1

I've installed Gnome 2.4 in my laptop, but I still haven't  been able to
configure docbook 2.4.1 for working with it.
I've tried to copy docbook.dtd in /etc/xml and editing the catalog  unsuccesfully,
in facts the system said that it "couldn' t locate docbook 4.2.1 XML"
Have someone a solution form my problem?
I think it will be enough to create the catalog, but in how?!
Tanks a lot.
Christian

__________________________________________________________________
Tiscali ADSL SENZA CANONE, paghi solo quello che consumi!
Navighi a 1,5 euro all'ora e il modem e' gratis! Abbonati subito.
http://point.tiscali.it/Adsl/prodotti/senzacanone/