Did you burn the disk yourself, at low burn speed, and confirm the MD5 checksum before you made the disc? The MD5 test is extremely important.

I don't know that particular computer, but if you can answer all of the above "yes" then you may need some hardware guidance to the program at boot time, referred to as cheat codes. Follow the documentation link near the top of this page and read the wiki article on cheat codes. A good first code to try is the failsafe code. You generally will not be happy with Knoppix booting that way, as it skips past a lot of hardware (including many mice) but at least if it boots in failsafe mode you will know that you just need to determine the right codes for your system (and if it doesn't then other cheat codes may not help you).

When you post back, tell us what version of Knoppix you really have 5.0 was only released in the German version at a trade show several years ago. 5.0.1, 5.1.0 and 5.1.1 are the designations for the various Internet releases before the current version, which is 5.3.1. Also post if you have the CD or DVD release and if you hane the DE or EN version.