These are the errors I am getting when I try to open techstream. I am running Big Sur and virtualbox verson 6.1.22I just installed on Catalina and will update to Big Sur tonight to verify it still works, but I don't see why it wouldn't. Just google "Virtualbox", click "Downloads", under the title "VirtualBox 6.1.22 platform packages" click on the "OS X Hosts" link, click the downloaded .dmg to install, launch VirtualBox simply to verify it works, then download and launch the Techstream .ova in the OP. Then you launch Techstream from VirtualBox after it has been installed, Windows XP 32-bit will boot and Techstream will have a desktop icon that you can launch.