hit f1 or f2 for more options before the 10 second timeout. maybe try different cheat codes/boot options. found these;http://www.slax.org/cheatcodes.phphttp://www.knoppix.net/wiki/Cheat_Codes
what version are you trying to run? can you decipher or write down the error code?
it may be that neither of these distros will run on your hardware. it may be easier to just try another distro. these are 2 completely different based distros. slax is slackware based. knoppix is debian based.
try PCLinuxOS. it's mandrake based. or ubuntu or mepis. these are debian based but may work.
probably hanging at detecting your video card or maybe nic card or modem.