The newest english version is: KNOPPIX_V3.3-2004-02-16-EN.iso
You will also want: KNOPPIX_V3.3-2004-02-16-EN.iso.md5
A howto for checking md5sums: http://www.linuxiso.org/viewdoc.php/verifyiso.html
And the FAQ for Knoppix is under the Docs section at the top of this page.