Absolutely great distro for donated, older pc's

I work for a non-profit agency. I fix up donated pc's for clients. Usually they are older and our clients are not computer literate. Kanotix installed perfectly - even the sound card worked right away. I downloaded some games and all the computers are wonderful. These older computers, Dell Optiplex barely a P3, look and run like a new pc's. The interface is attractive and easy to use.
My students love this distro and most of them have little computer experience.
Thank you!