With Hyper-V, basically I set up TC 9, copied (via export and import) it and started making changes to the copy. I then decided I wanted to try to install TC10. During the install process, 'sda' was not present. Deleting my other VMs, uninstalling/reinstalling Hyper-V did not help. After uninstalling Hyper-V, I was able to "set-up" TC10 on Virtualbox, and in the first screen of the TC-install, sda was present, but otherwise, Virtualbox was conflicting with Hyper-V during the set-up of the VM.
Anyways, what happened to sda? Why does it not show? How can I get it back? In the install GUI, where sda should be, I can click on the choice as if there's a choice there, but it's blank.