Questions about Knoppix: (low-mem computer, screen switching off...)

Hi
I'm using Knoppix on a very old computer, a Toshiba Satellite 4070CDS. 
First, I've got some problem... the screen switches off in a while (2 minutes 
or so) if I don't touch any key, even if I move the mouse. Why can this be 
happening? Is this related to acpi?

And then a little off-topic, do you know where can I find a place with some 
advices for a low-mem (64MB), low-cpu (celeron 200) computer running KDE? 
What should I disable, what should I activate, etc? (for example, I remember 
some time ago, when I drag&drop a window, I only moved the silhouette of the 
window until I released the mouse button, and in this moment the windows was 
moved, something like that)

Thanks