Thanks for your comment.
I have tried to reboot from the Windows 8 Install DVD so that I can access the repair link, but have not been able to force the VM to boot from it. I have tried Esc, changing the boot device to no avail. Do you know of another way to force the VM to boot from the attached DVD?
I have also tried to repair the disk using diskchk in Win but it can't do it because the disk is read-only.
How can I tell if the disk issue is a VM problem or a Win problem?
Thanks