VMWare will do your job, but as it will be emulating the OS from within your present one, it will be quite slow. You can use this article to directly boot into the ISO, if you have access to DOS (A bootable floppy will do) -
*www.damnsmalllinux.org/talk/node/191
This is intended for Damn Smal Linux, which is based off knoppix. It can easily be adapted to work with knoppix, if you want any help on that, please post here
By the way please post linux related queries in the open source section.