From a review of ''mini-distros'' published in Linux Format Magazine about 6 months ago I seem to recall that Mu Linux (available via the page for which Bob provided a link) may have a GUI (of sorts - more akin to a DOS ''Shell'').
I seem to recall from the article that it could run using 12 Mb RAM.
I read this magazine article with interest as I often try to utilise older hardware and as a result discovered Damn Small Linux, Feather Linux, and Puppy Linux which require between a minimum of 24mb (for DSL) and 32mb (for Feather & Puppy).
If you could double your RAM then DSL might also provide an option (I would suggest that you try version 1 or 1.5 in the first instance).
Ms-DOS (& many other dos') will run on just about anything and one advantage is the huge amount of free software availble via the web for FREE.
I am sorry that I cannot be more specific about Mu Linux but I have donated that magazine to my Doctors surgery about a month ago and therefore I cannot verify the specification required.
Trevor