This article is incomplete and was first written in June 2006 
for the BeezNest technical website (http://glasnost.beeznest.org/articles/336).
This is a procedure to upgrade a Debian Sarge GNOME Desktop PC to Debian  Etch.
First, make sure you are not using devfs. If you are using udev, or no  device manager daemon, then you are ready. Also, I did not test upgrade  from a 2.4 kernel, only 2.6 to 2.6.
Make sure all your packages belong to well-known apt sources, otherwise,  you will probably have to fix things by hands later. 
apt-show-versions is a tool that could be helpful for this.
Replace all occurences to 
sarge (or 
stable) in /etc/apt/sources.list  by 
etch.
# apt-get update
The first tricky part is to get kernel and udev working fine. Hope you  don't have any third-party kernel module needed for the upgrade (wifi driver?).  Any module included officially in the kernel will do, though.
Preferably stop all of your running applications, logoff, and stop gdm (you're using gdm, right?). Then:
# touch /etc/udev/kernel-upgrade
# apt-get install udev initramfs-tools linux-image-2.6-686
# apt-get install modutils module-init-tools apt aptitude tasksel
As you've just upgraded apt, rerun an apt-get update before continuing.Remove the 
hotplug, 
modutils and 
base-config packages, they are no longer used
# dpkg -P hotplug modutils base-config
# apt-get install gnome-volume-manager