Souces.list necessary mirrors
 

I'm having a debian gnome installation. Can you tell me the necessary mirrors Ixshould put in it?

You don't mention which version of Debian. You'll want a main deb and a deb-src for your version, as well as security updates if you're running stable or testing. Past that you can add any third-party repositories you want like debian-multimedia.

I'm ruunig debian lenny, I think. How do I check it? And if you can tell me, what's the difference between lenny and etch?

In a terminal type
BTW, there is a thread with sources lists.
http://www.linuxquestions.org/questi...ht=source+list