What version of .Net does the computer you're trying to run this on have installed? If possible, I would installed the latest versions
Basically, what this error is telling you is that the program requested a class from the registry, which makes me think there's something that is not installed on the computer that's required to run Virtual Box Portable.
Did you ever get to the "Portable-VirtualBox *** Extract and/or Compress ***" window?
Edit:
Okay, next thought - it looks like you're running Windows 7. Do you have UAC disabled? VirtualBox is probably trying to register a COM object with the OS, and without administrative permissions, it won't be able to. I would try running the portable exe as an administrator (right-click -> Run as administrator) or, if it's disabled, enabling UAC and see if that helps.