[CLUE-Tech] Burning Knoppix ISO with XCDroast?

[Joe Linux]

I have downloaded the 1-20-2003 Knoppix ISO image and done an md5sum 
check and every thing is in order.  When I burn the downloaded image 
with XCDroast, I don't get something that's bootable.  I get an exact 
copy of the file I downloaded rather than the file directories that you 
are supposed to get with a CD that works.  Does anyone know what I might 
be doing wrong?  I know that in the past you had to rename the file with 
some other extension before burning it.  Any help would be greatly 
appreciated.