1. VirtualBox is installed by default in Knoppix7.4.2
2. This VirtualBox and Knoppix7.4.2 itself are basically 32-bit except as I noted earlier.
3. No 64 bit apps, including those emulated in Virtual box are supported by the necessary libraries in Knoppix 7.4.2
4. There is virtually no 64-bit library support in Knoppix 7.4.2

If you insist on needing 64-bit support for your apps, you currently need another distribution or
as I suggested elsewhere, try some of the work-arounds tha Capricorny and others have discussed here.

All my previous comments apply only to an unmodified Knoppix 7.4.2 LiveUSB install, please be advised.
If you have tried to 'upgrade' Knoppix 7.4.2 with Synaptic or apt-get, it is quite likely you will arrive at
a broken and unusable Knoppix system. This is also likely if you try to bring in programs from other repos
without regard to version compatiblities.