All are Sarge. Sid is what you get if you want to use the unstable version of Debian.
Try Sarge first, then, if you need more recent software, upgrade to Sid by changing your
sources (repositories) in the file called /etc/apt/sources.list
Simply replace the 'stable' mention in this file by 'unstable', run apt-get update and there
you go, at your own risk...
EDIT : better not do that with a 2.4 kernel...