Shoutbox

I've tried running Linux on lower end PCs, and it wasn't too much fun. If you tried Xubuntu and didn't like it, that means you don't like the XFCE window manager - I think it's alright, but it's by far and away the most lightweight of the three main ones (KDE, GNOME being the other two).

Knoppix uses KDE as the front-end. If you want to try KDE with ubuntu, try getting Kubuntu. Personally, I wouldn't run newer versions of KDE on anything less than 256MB of RAM, but it's worth a shot.

If you can find it, and older version of RedHat 8/9 might be worth looking into.