There are GUIs with lower memory needs than KDE. icewin is often mentioned for Knoppix (warning: I've never used it, so I am not giving advice to use it). But the wisdom of installing Knoppix at all is questionable. I have two suggestions to offer:

  • 1) Post your actual system specs so that people can know what the target system is. To some people an "old" system is a 1 ghz Athlon with a 60 gig hard drive, to others it is a 25 mhz 386 (or older CPU) and 8 megs of RAM. Linux can run on either (Knoppix will not), but we can not give good advice without knowing the target system.

    2) Consider installing Debian rather than Knoppix. You will avoid the well known Knoppix install problems. You can install a less demanding GUI like Gnome (if you have the resources for that). You can install exactly the UI and other applications that you want, and you don't end up installing lots of applications that you don't want and will never use (saving resources).