Credo di avere etch...come imposto stable?

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# deb cdrom:[Debian GNU/Linux 4.0 r4a _Etch_ - Official i386 NETINST Binary-1 20080804-15:10]/ etch contrib main

deb cdrom:[Debian GNU/Linux 4.0 r4a _Etch_ - Official i386 NETINST Binary-1 20080804-15:10]/ etch contrib main

deb http://ftp.it.debian.org/debian/ etch main
deb-src http://ftp.it.debian.org/debian/ etch main

deb http://security.debian.org/ etch/updates main contrib
deb-src http://security.debian.org/ etch/updates main contrib