sources.list:

#deb file:///cdrom/ sarge main

#sarge
deb http://security.debian.org/ stable/updates main contrib
deb ftp://ftp.tu-ilmenau.de/mirror/debian/debian sarge main contrib non-free
deb http://security.debian.org sarge/updates main contrib non-free
deb ftp://ftp.tu-ilmenau.de/mirror/debian/debian sarge main contrib non-free

#etch
deb http://security.debian.org/ testing/updates main contrib
deb ftp://ftp.tu-ilmenau.de/mirror/debian/debian etch main contrib non-free
deb http://security.debian.org etch/updates main contrib non-free
deb-src ftp://ftp.tu-ilmenau.de/mirror/debian/debian etch main contrib non-free
~


pref:

Package: *
Pin: release a=stable
Pin-Priority: 700

Package: *
Pin: release a=testing
Pin-Priority: 650

Package: *
Pin: release a=unstable
Pin-Priority: 600