Linux is very small, gnome or kde less so (but still smaller than the mainstream alternatives). Depending how far you want to go down the usability vs. memory usage route, you could try Gnome with as many features turned off as you can stand, or evilwm (a windowmanager that uses 1/3 as much RAM as the bash shell), or any one of the literally hundreds of other options. With evilwm, a solid color on the desktop, vanilla sh instead of bash, and vanilla vi or qemacs instead of vim or emacs, you could run a whole system on a 386 if you really wanted to, and could figure out what to do with it without gnome holding your hand.