It is the first thing you need to fix the issue as stated above. For that, you need to run the virtual machine showing the error and go to the Devices > Install Guest ...

Virtualbox is a great app for using different operating systems on your PC, so here's how to get a fresh virtual machine set up and running.

As our home computers become more robust, we can do more powerful things with them. Virtualization isn't new; it's almost as old as computers themselves, but the ability to run virtualization ...