Dear All,
Even though it's not very common, you may still face some problems when you try to install Kali Linux for the first time and actually I mention most of the problems and solutions in the course. However it might be a good idea to list some generic solutions for you. You have to specifically control the Error Details from Virtualbox if you get any error to follow this list.
Solutions:
1) I'm getting vt-x disabled, virtualization disabled error!
You should enable virtualization technology from your BIOS settings. In order to do that, restart your computer. Before your operating system loads, it should show you a key to get into BIOS settings such as F12, Delete, F8 etc. You have to go into BIOS and find a setting related to virtualization. It should appear as V-tx, Intel Virtualization Technology, Virtualization, SVM etc. If you cannot find it, I suggest you google your own processor and computer model in order to find out how to enable virtualization on your setup.
If that doesn't work, you should look for Hyper-V in your Windows and disable it as well.
2) 64 bit is not shown in the list even though I installed 64 bit version.
You should do the same thing on Question 1.
3) I start the virtual machine but it gets stuck on a black screen
You should do the same thing on Question 1.
4) I do the same thing on Question 1 but it's already enabled
You should check to see if Debian 64 bit is chosen. If it is you may try to increase the allocated RAM.
5) My BIOS screen is too old I cannot find a way to update it
Kindly refer here: https://www.wikihow.com/Update-Your-Computer%27s-BIOS
6) I'm getting a "USB 2.0 Not Found" error!
It means that extension pack is not properly installed. Please try and install extension pack one more time.
7) I'm getting a "Linux Fatal: No Bootable Medium Found" error!
Kindly refer here: https://www.youtube.com/watch?v=h90BWSYgL5Q
8) I couldn't run Kali Linux no matter what!
You can try to manually set Kali Linux up with .iso file as shown in here: http://www.wikigain.com/install-kali-linux-virtualbox-pc/
Official webpage to download .iso file: https://www.kali.org/downloads/