It has been nearly a year since the last public release of Knoppix, which coupled with a new stable release of Debian earlier this year means just about every package included in Knoppix is an old version. When I did a clean install on my new laptop(since using partimage to clone my old laptop's root partition didn't work), it took me most of a weekend just to do the most basic of my customizations(namely, marking every package as automatically installed and going through Aptitude's auroremove list to mark stuff I need as manually installed, and upgrading packages left by the big purge who would upgrade without Aptitude complaining, and even that much is beyond what I could in good conscious recommend to a newbie). Given the large number of packages in 7.4.2 that are out-of-date, unless you really know what you are doing, you might be better off sticking with the older versions and wait until 7.6 comes out to try an install that is kept up-to-date. If you do try either upgrading everything that is installed or purging stuff you don't need, I'd recommend doing it in phases rather than all at once. Also, for what it's worth, I'm pretty sure the default version of Iceweasel is already a newer version than the one found in Jessy(the pre-installed version being 32.something whereas Jessy runs 31.something(granted, I think Iceweasel 31 is a long term support version while Iceweasel 32 is a minor release, so the version in Jessie might have more security fixes).