A portable Virtualbox is the portable version of Oracle Virtualbox software. It works similar to VM-ware, but it is completely free. You can install this portable version on your Pendrive preferred space. You can run virtually any OS on this Pendrive without using additional software installation or booting from the Pendrive.
According to Vbox.me:
"Portable-VirtualBox makes default settings automatically. You can modify them by pressing CTRL-5 or opening the tray menu while Portable-VirtualBox is running. Either action will bring up the configuration GUI below:"
Features
(the above features and images were copied directly from https://www.vbox.me/)
Note: When the v-box is completely installed, open the portable-
vbox.exe
file. Once it opens, close it immediately and then give it some time to auto-configure. Open and use it after some time.To install the Kali Linux in the newly installed v-box, you can use kali via the live image from kali.org.
Now after downloading the kali image, configure it as you do on the normal v-box. Then after everything is done, you can access the OS from the Pendrive.
Here is a video by avoiderrors on youtube. I recommend this video as it covers all the necessary points.