Operating Systems for really, really old computers.!!

H

Nice list here

Not Linux but worth mentioning
(<2Mb) KolibriOS (based on MenuetOS) a GUI OS
(~11Mb) FreeDOS + OpenGEM - DOS compatible GUI
(~23Mb) ReactOS - Windows compatible but still in alpha
(~30Mb) KolibriOS CD version (based on MenuetOS) a GUI OS

Under 50Mb
Distros under 50Mb fit onto a MiniCD.

(~3Mb) Mungkie - (aka 2diskXwin)
(12Mb) Grey Cat Linux - Slackware based with IceWM
(<15Mb) SliTaz with JWM
(<50Mb) DamnSmallLinux - based on Knoppix, but with Fluxbox
(44Mb) Jinx - with Opera 9, Flash, Textmaker and Planmaker.
(<50Mb) Austrumi - A business card size bootable live CD Linux distribution based on Slackware.
(<50Mb) MeanPup -A live distro based on Puppy
(<50Mb) Mitrax -A live distro based on Slackware
(<50Mb) Luit - XFCE and ROXFile

Under 128Mb

(<100Mb) NimbleX sub100 - Slackware based with KDE
(<100Mb) Puppy Linux - live with IceWM (see also eBoxPup, IcePup, LitePup, MiniPup, PizzaPup, SafePup and XPuppyPro)
(84Mb) DamnSmallLinux-Not - distro using Knoppix hardware recognition with Abiword and Gnumeric.
(<128Mb) DeLi - Desktop Light
(<128Mb) SLAX Popcorn Edition- A smaller version of SLAX with Xfce
(<128Mb) FeatherLinux - Knoppix based distro with Fluxbox

Under 256Mb

(177Mb) TinyMe - based on pcLinuxOS, but with Openbox
(182Mb) Kurumin 6 Light - Knoppix based, with KDE
(~200Mb) PUD - based on Ubuntu
(~200Mb) Slax - Distro based on Slackware using KDE
(223Mb) TinyFlux - based on TinyMe, with Fluxbox
(230Mb) Kanotix CpxMini, Kanotix, but with Fluxbox
(241Mb) Wolvix Cub
(<250Mb) Featherweight- based on Feather Linux, but with KDE
(<256Mb) Flash Linux- Gentoo-based, initially designed to run off of a 256Mb USB key.

Under 700Mb
Distros under 700Mb fit onto most CD-Rs. These should still run in 128Mb RAM on a Pentium III level machine.

(278Mb) AliXe - Slax based with Xfce
(300Mb) Fluxbuntu - Ubuntu 7.10 based with Fluxbox
(410Mb) AntiX - MEPIS based with Fluxbox
(551Mb) Kanotix Lite with KDE
(614Mb) SaxenOS 1 - with EDE
(626Mb) MEPISLite - MEPIS based with KDE
(662Mb) eLive - Debian based with Enlightenment
(699Mb) SAM - A LiveCD based on PCLinuxOS, but with Xfce.