Cannot mount ISO in CentOS 7 Guest running rescue kernel

I have a CentOS 7-Minimal VM running on a Windows 7 host that has been happily running for a year or so. A kernel panic occurred and I was unable to boot into anything except the rescue kernel. While trying to troubleshoot the panic, I removed (via yum remove) all the other installed kernels and was going to simply reinstall the latest. However, for some reason I cannot mount any ISO file (CentOS, VBox GuestAdditions, etc) to install the kernel package. Attempting to mount an ISO doesn't recognize the file system: The drive is attached: I hope I am missing something simple, but I've spent half a day trying to get this working to no avail.