non-system disk error

What is wrong? I'm trying to load knoppix 3.4, but i keep getting the "non-system disk" error. I've burned my cd using Nero 5 with 3 files:

KNOPPIX_V3.4-2004-05-17-EN.iso
KNOPPIX_V3.4-2004-05-17-EN.iso.md5
KNOPPIX_V3.4-2004-05-17-EN.iso.md5.asc

Is this correct or am I missing something?

It sounds like you burned the three files you mentioned as data to a CD, rather than burning the ISO as a CD image. (Common mistake.) Look for the "Burn image..." choice on the "File" menu in Nero 5. Select your ISO file.

Thanks. It now works.