I've tried a lot of different things already. For a synopsis of what caused the problem, please see this unanswered question on Unix/Linux stack exchange. Basically, I'm on a Windows 10 host and I have an unbootable CentOS 7 VM on Virtual Box. I need to know how to recover files from my unbootable VDI.
I've read this question (and many others), for which creating a new profile for the VM didn't fix it. I'm also unsure how a rescue disk would fix it--very unclear instructions. I've tried several different discontinued softwares. I've also tried "mounting" the virtual disk through VirtualBox in a brand new CentOS installation (that just...didn't work; it thought I wanted to boot from the old one).
I feel like I've exhausted everything I can find on the Internet, so I might as well raise a duplicate question.