A client recently got in touch for our help with Hyper-V Manager. After moving virtual server, they continually received “An error occurred while attempting to start the selected virtual machine(s).” when attempting to boot it up. No changes had been made to the Windows Server OS in the VM, but it refused to boot with x failed to start.
When this happens: Edit the VM Settings and add a new hard disk.
In many cases, this step will get you up and running again right away.