I would suggest starting by following the Documentation link near the top of this page and reading the Downloading FAQ portion of the wiki. We really don't have enough information to tell you exactly what is wrong. If I had to make a guess I would try that perhaps your system needs one or more "cheat codes" to help it boot, and I would further guess that you might benefit from xmodule=vesa or one of the other xmodule codes, but that is only a guess since we don't have enough to go on. We are not even sure if you checked the md5 checksum before burning the disc, burnt it at low speed, and otherwise made it correctly, or even of which Knoppix version you are using and what hardware you are running on.

So start by reviewing the downloadng FAQ, it should cover all of the steps for making and booting a Knoppix disc. There is also a wiki section explaining cheat codes, although if you downloaded by the torrent then you already have a good cheat code document.