Most compelling limitation on old laptops is HD size. Knoppix needs 2.4 Gig just to install, if your laptop is old enough to only have a 2 G HD (ie..from the win98 era) you just don't have enough HD space to install Knoppix except as a poormans install. My 600 Mhz Toshiba (originally winME) has 6G & I can fit Knoppix & winME dual boot on it.