You are right. VirtualBox needs to load several Windows kernel drivers to function. So if the drivers are not already installed you’ll need administrator rights

You are right. VirtualBox needs to load several Windows kernel drivers to function. So if the drivers are not already installed you’ll need administrator rights to run it. Portable-VirtualBox loads and then unloads this drivers when you use it, so it isn't truly portable in that way. There are no way around this if you want to run the quest os directly on the cpu as VirtualBox dos. Otherwise you would have to use a emulator like Qemu, but then you would only get 1/20 of the speed or so.