There is no simple answer to "best distro". There are plenty of factors, including what you want to do with the system and personal choices that come into play. You give a lot of specs, but seem to leave out the amount of memory of the system (in megs). Also, you say that there is a co-processor, but the P133 has the math processor built in. Are you telling us there is some other sort of co-processor or are you just reafirming the math processor that we all know is part of a Pentium? You certainly should be able to install Debian to this system (likely can't install Knoppix except a "poor man's install" since the disk is so small and it hardly ever goes well any way.