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.

VirtualBox is great for testing out a new operating system, but your virtual machines probably aren't that special when you first set them up. Here are a few tips for making them much easier to ...